From 66ada54280ee41a654c72809e1ad3fd1e401f780 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 22 Apr 2019 15:02:52 -0700
Subject: [PATCH 01/40] Java side of FirebasePerformance rewrite

---
 .../FirebasePerformancePlugin.java            | 154 +-----------------
 .../FlutterFirebasePerformance.java           |  62 +++++++
 .../FlutterHttpMetric.java                    | 113 +++++++++++++
 .../firebaseperformance/FlutterTrace.java     | 134 +++++++++++++++
 4 files changed, 313 insertions(+), 150 deletions(-)
 create mode 100644 packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
 create mode 100644 packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
 create mode 100644 packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
index cd8d4960fd16..ad115a499d2f 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
@@ -4,161 +4,15 @@
 
 package io.flutter.plugins.firebaseperformance;
 
-import android.util.SparseArray;
-import com.google.firebase.perf.FirebasePerformance;
-import com.google.firebase.perf.metrics.HttpMetric;
-import com.google.firebase.perf.metrics.Trace;
-import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
-import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
-import io.flutter.plugin.common.MethodChannel.Result;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
-import java.util.Map;
 
 /** FirebasePerformancePlugin */
-public class FirebasePerformancePlugin implements MethodCallHandler {
-  private FirebasePerformance firebasePerformance;
-
-  private final SparseArray<Trace> traces = new SparseArray<>();
-  private final SparseArray<HttpMetric> httpMetrics = new SparseArray<>();
+public class FirebasePerformancePlugin {
+  private static final String CHANNEL_NAME = "plugins.flutter.io/firebase_performance";
 
   public static void registerWith(Registrar registrar) {
-    final MethodChannel channel =
-        new MethodChannel(registrar.messenger(), "plugins.flutter.io/firebase_performance");
-    channel.setMethodCallHandler(new FirebasePerformancePlugin());
-  }
-
-  private FirebasePerformancePlugin() {
-    firebasePerformance = FirebasePerformance.getInstance();
-  }
-
-  @Override
-  public void onMethodCall(MethodCall call, Result result) {
-    switch (call.method) {
-      case "FirebasePerformance#isPerformanceCollectionEnabled":
-        result.success(firebasePerformance.isPerformanceCollectionEnabled());
-        break;
-      case "FirebasePerformance#setPerformanceCollectionEnabled":
-        final boolean enabled = (boolean) call.arguments;
-        firebasePerformance.setPerformanceCollectionEnabled(enabled);
-        result.success(null);
-        break;
-      case "Trace#start":
-        handleTraceStart(call, result);
-        break;
-      case "Trace#stop":
-        handleTraceStop(call, result);
-        break;
-      case "HttpMetric#start":
-        handleHttpMetricStart(call, result);
-        break;
-      case "HttpMetric#stop":
-        handleHttpMetricStop(call, result);
-        break;
-      default:
-        result.notImplemented();
-    }
-  }
-
-  private void handleTraceStart(MethodCall call, Result result) {
-    Integer handle = call.argument("handle");
-    String name = call.argument("name");
-
-    Trace trace = firebasePerformance.newTrace(name);
-
-    traces.put(handle, trace);
-
-    trace.start();
-    result.success(null);
-  }
-
-  private void handleTraceStop(MethodCall call, Result result) {
-    Integer handle = call.argument("handle");
-    Trace trace = traces.get(handle);
-
-    Map<String, Integer> counters = call.argument("counters");
-    for (Map.Entry<String, Integer> entry : counters.entrySet()) {
-      trace.incrementCounter(entry.getKey(), entry.getValue());
-    }
-
-    Map<String, String> attributes = call.argument("attributes");
-    for (Map.Entry<String, String> entry : attributes.entrySet()) {
-      trace.putAttribute(entry.getKey(), entry.getValue());
-    }
-
-    trace.stop();
-    traces.remove(handle);
-    result.success(null);
-  }
-
-  private void handleHttpMetricStart(MethodCall call, Result result) {
-    Integer handle = call.argument("handle");
-    String url = call.argument("url");
-
-    int httpMethod = call.argument("httpMethod");
-    String httpMethodStr;
-    switch (httpMethod) {
-      case 0:
-        httpMethodStr = FirebasePerformance.HttpMethod.CONNECT;
-        break;
-      case 1:
-        httpMethodStr = FirebasePerformance.HttpMethod.DELETE;
-        break;
-      case 2:
-        httpMethodStr = FirebasePerformance.HttpMethod.GET;
-        break;
-      case 3:
-        httpMethodStr = FirebasePerformance.HttpMethod.HEAD;
-        break;
-      case 4:
-        httpMethodStr = FirebasePerformance.HttpMethod.OPTIONS;
-        break;
-      case 5:
-        httpMethodStr = FirebasePerformance.HttpMethod.PATCH;
-        break;
-      case 6:
-        httpMethodStr = FirebasePerformance.HttpMethod.POST;
-        break;
-      case 7:
-        httpMethodStr = FirebasePerformance.HttpMethod.PUT;
-        break;
-      case 8:
-        httpMethodStr = FirebasePerformance.HttpMethod.TRACE;
-        break;
-      default:
-        httpMethodStr = null;
-        break;
-    }
-
-    HttpMetric metric = firebasePerformance.newHttpMetric(url, httpMethodStr);
-
-    httpMetrics.put(handle, metric);
-
-    metric.start();
-    result.success(null);
-  }
-
-  private void handleHttpMetricStop(MethodCall call, Result result) {
-    Integer handle = call.argument("handle");
-    HttpMetric metric = httpMetrics.get(handle);
-
-    Integer httpResponseCode = call.argument("httpResponseCode");
-    Number requestPayloadSize = call.argument("requestPayloadSize");
-    String responseContentType = call.argument("responseContentType");
-    Number responsePayloadSize = call.argument("responsePayloadSize");
-
-    if (requestPayloadSize != null) metric.setRequestPayloadSize(requestPayloadSize.longValue());
-    if (httpResponseCode != null) metric.setHttpResponseCode(httpResponseCode);
-    if (responseContentType != null) metric.setResponseContentType(responseContentType);
-    if (responsePayloadSize != null) metric.setResponsePayloadSize(responsePayloadSize.longValue());
-
-    Map<String, String> attributes = call.argument("attributes");
-    for (Map.Entry<String, String> entry : attributes.entrySet()) {
-      metric.putAttribute(entry.getKey(), entry.getValue());
-    }
-
-    metric.stop();
-    httpMetrics.remove(handle);
-    result.success(null);
+    final MethodChannel channel = new MethodChannel(registrar.messenger(), CHANNEL_NAME);
+    channel.setMethodCallHandler(FlutterFirebasePerformance.getInstance(registrar.messenger()));
   }
 }
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
new file mode 100644
index 000000000000..bc3da7ea53f9
--- /dev/null
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
@@ -0,0 +1,62 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.firebaseperformance;
+
+import com.google.firebase.perf.FirebasePerformance;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+
+public class FlutterFirebasePerformance implements MethodChannel.MethodCallHandler {
+  private final BinaryMessenger binaryMessenger;
+  private final FirebasePerformance performance;
+
+  static FlutterFirebasePerformance getInstance(BinaryMessenger messenger) {
+    return new FlutterFirebasePerformance(messenger);
+  }
+
+  private FlutterFirebasePerformance(BinaryMessenger messenger) {
+    this.binaryMessenger = messenger;
+    this.performance = FirebasePerformance.getInstance();
+  }
+
+  @Override
+  public void onMethodCall(MethodCall call, MethodChannel.Result result) {
+    switch (call.method) {
+      case "FirebasePerformance#isPerformanceCollectionEnabled":
+        isPerformanceCollectionEnabled(result);
+        break;
+      case "FirebasePerformance#setPerformanceCollectionEnabled":
+        setPerformanceCollectionEnabled(call.arguments, result);
+        break;
+      case "FirebasePerformance#newTrace":
+        newTrace(call.arguments, result);
+        break;
+      case "FirebasePerformance#newHttpMetric":
+        newHttpMetric(call.arguments, result);
+        break;
+      default:
+        result.notImplemented();
+    }
+  }
+
+  private void isPerformanceCollectionEnabled(MethodChannel.Result result) {
+    result.success(performance.isPerformanceCollectionEnabled());
+  }
+
+  private void setPerformanceCollectionEnabled(Object arguments, MethodChannel.Result result) {
+    final boolean enabled = (Boolean) arguments;
+    performance.setPerformanceCollectionEnabled(enabled);
+    result.success(null);
+  }
+
+  private void newTrace(Object arguments, MethodChannel.Result result) {
+    new FlutterTrace(performance, binaryMessenger, arguments, result);
+  }
+
+  private void newHttpMetric(Object arguments, MethodChannel.Result result) {
+    new FlutterHttpMetric(performance, binaryMessenger, arguments, result);
+  }
+}
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
new file mode 100644
index 000000000000..1d2e8a3729af
--- /dev/null
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -0,0 +1,113 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.firebaseperformance;
+
+import com.google.firebase.perf.FirebasePerformance;
+import com.google.firebase.perf.metrics.HttpMetric;
+import java.util.Map;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+
+public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
+  private final HttpMetric httpMetric;
+
+  FlutterHttpMetric(
+      FirebasePerformance performance,
+      BinaryMessenger messenger,
+      Object arguments,
+      MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String channelName = (String) args.get("channelName");
+    final String url = (String) args.get("url");
+    final String httpMethod = (String) args.get("httpMethod");
+
+    this.httpMetric = performance.newHttpMetric(url, httpMethod);
+
+    final MethodChannel channel = new MethodChannel(messenger, channelName);
+    channel.setMethodCallHandler(this);
+
+    result.success(null);
+  }
+
+  @Override
+  public void onMethodCall(MethodCall call, MethodChannel.Result result) {
+    switch (call.method) {
+      case "HttpMetric#start":
+        start(result);
+        break;
+      case "HttpMetric#stop":
+        stop(call.arguments, result);
+        break;
+      case "PerformanceAttributes#putAttribute":
+        putAttribute(call.arguments, result);
+        break;
+      case "PerformanceAttributes#removeAttribute":
+        removeAttribute(call.arguments, result);
+        break;
+      case "PerformanceAttributes#getAttributes":
+        getAttributes(result);
+        break;
+      default:
+        result.notImplemented();
+    }
+  }
+
+  private void start(MethodChannel.Result result) {
+    httpMetric.start();
+    result.success(null);
+  }
+
+  private void stop(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final Integer httpResponseCode = (Integer) args.get("httpResponseCode");
+    final Number requestPayloadSize = (Number) args.get("requestPayloadSize");
+    final String responseContentType = (String) args.get("responseContentType");
+    final Number responsePayloadSize = (Number) args.get("responsePayloadSize");
+
+    if (requestPayloadSize != null) {
+      httpMetric.setRequestPayloadSize(requestPayloadSize.longValue());
+    }
+    if (responsePayloadSize != null) {
+      httpMetric.setResponsePayloadSize(responsePayloadSize.longValue());
+    }
+
+    if (httpResponseCode != null) httpMetric.setHttpResponseCode(httpResponseCode);
+    if (responseContentType != null) httpMetric.setResponseContentType(responseContentType);
+
+    httpMetric.stop();
+    result.success(null);
+  }
+
+  private void putAttribute(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String attribute = (String) args.get("attribute");
+    final String value = (String) args.get("value");
+
+    httpMetric.putAttribute(attribute, value);
+
+    result.success(null);
+  }
+
+  private void removeAttribute(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String attribute = (String) args.get("attribute");
+    httpMetric.removeAttribute(attribute);
+
+    result.success(null);
+  }
+
+  private void getAttributes(MethodChannel.Result result) {
+    result.success(httpMetric.getAttributes());
+  }
+}
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
new file mode 100644
index 000000000000..3ccbfdd07b14
--- /dev/null
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -0,0 +1,134 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.firebaseperformance;
+
+import com.google.firebase.perf.FirebasePerformance;
+import com.google.firebase.perf.metrics.Trace;
+import java.util.Map;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+
+public class FlutterTrace implements MethodChannel.MethodCallHandler {
+  private final Trace trace;
+
+  FlutterTrace(
+      FirebasePerformance performance,
+      BinaryMessenger messenger,
+      Object arguments,
+      MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String traceName = (String) args.get("traceName");
+    final String channelName = (String) args.get("channelName");
+
+    this.trace = performance.newTrace(traceName);
+
+    final MethodChannel channel = new MethodChannel(messenger, channelName);
+    channel.setMethodCallHandler(this);
+
+    result.success(null);
+  }
+
+  @Override
+  public void onMethodCall(MethodCall call, MethodChannel.Result result) {
+    switch (call.method) {
+      case "Trace#start":
+        start(result);
+        break;
+      case "Trace#stop":
+        stop(result);
+        break;
+      case "Trace#putMetric":
+        putMetric(call.arguments, result);
+        break;
+      case "Trace#incrementMetric":
+        incrementMetric(call.arguments, result);
+        break;
+      case "Trace#getMetric":
+        getMetric(call.arguments, result);
+        break;
+      case "PerformanceAttributes#putAttribute":
+        putAttribute(call.arguments, result);
+        break;
+      case "PerformanceAttributes#removeAttribute":
+        removeAttribute(call.arguments, result);
+        break;
+      case "PerformanceAttributes#getAttributes":
+        getAttributes(result);
+        break;
+      default:
+        result.notImplemented();
+    }
+  }
+
+  private void start(MethodChannel.Result result) {
+    trace.start();
+    result.success(null);
+  }
+
+  private void stop(MethodChannel.Result result) {
+    trace.stop();
+    result.success(null);
+  }
+
+  private void putMetric(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String name = (String) args.get("name");
+    final Number value = (Number) args.get("value");
+    trace.putMetric(name, value.longValue());
+
+    result.success(null);
+  }
+
+  private void incrementMetric(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String name = (String) args.get("name");
+    final Number value = (Number) args.get("value");
+    trace.incrementMetric(name, value.longValue());
+
+    result.success(null);
+  }
+
+  private void getMetric(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String name = (String) args.get("name");
+
+    result.success(trace.getLongMetric(name));
+  }
+
+  private void putAttribute(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String attribute = (String) args.get("attribute");
+    final String value = (String) args.get("value");
+
+    trace.putAttribute(attribute, value);
+
+    result.success(null);
+  }
+
+  private void removeAttribute(Object arguments, MethodChannel.Result result) {
+    @SuppressWarnings("unchecked")
+    final Map<String, Object> args = (Map<String, Object>) arguments;
+
+    final String attribute = (String) args.get("attribute");
+    trace.removeAttribute(attribute);
+
+    result.success(null);
+  }
+
+  private void getAttributes(MethodChannel.Result result) {
+    result.success(trace.getAttributes());
+  }
+}

From 784ebc178e06a7f6c7fc2930c744eec0fd2634c1 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 22 Apr 2019 15:07:28 -0700
Subject: [PATCH 02/40] Performance rewrite dart side

---
 .../example/lib/main.dart                     |   2 +-
 .../lib/firebase_performance.dart             |   1 -
 .../lib/src/firebase_performance.dart         |  62 ++++-----
 .../lib/src/http_metric.dart                  |  71 ++---------
 .../lib/src/performance_attributes.dart       |  39 +++---
 .../firebase_performance/lib/src/trace.dart   | 118 ++++++------------
 6 files changed, 103 insertions(+), 190 deletions(-)

diff --git a/packages/firebase_performance/example/lib/main.dart b/packages/firebase_performance/example/lib/main.dart
index b9c46614748b..d81e951faaf0 100644
--- a/packages/firebase_performance/example/lib/main.dart
+++ b/packages/firebase_performance/example/lib/main.dart
@@ -77,7 +77,7 @@ class _MyAppState extends State<MyApp> {
     });
 
     final Trace trace = _performance.newTrace("test");
-    trace.incrementCounter("counter1", 16);
+    trace.putMetric("counter1", 16);
     trace.putAttribute("favorite_color", "blue");
 
     await trace.start();
diff --git a/packages/firebase_performance/lib/firebase_performance.dart b/packages/firebase_performance/lib/firebase_performance.dart
index 17dbcfc07863..8f8a2e7a4348 100644
--- a/packages/firebase_performance/lib/firebase_performance.dart
+++ b/packages/firebase_performance/lib/firebase_performance.dart
@@ -5,7 +5,6 @@
 library firebase_performance;
 
 import 'dart:async';
-import 'dart:collection';
 
 import 'package:flutter/services.dart';
 import 'package:flutter/foundation.dart';
diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index 381236d44dc7..165ed0851f87 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -13,9 +13,6 @@ enum HttpMethod { Connect, Delete, Get, Head, Options, Patch, Post, Put, Trace }
 class FirebasePerformance {
   FirebasePerformance._();
 
-  static int _traceCount = 0;
-  static int _httpMetricCount = 0;
-
   @visibleForTesting
   static const MethodChannel channel =
       MethodChannel('plugins.flutter.io/firebase_performance');
@@ -23,30 +20,28 @@ class FirebasePerformance {
   /// Singleton of [FirebasePerformance].
   static final FirebasePerformance instance = FirebasePerformance._();
 
+  static int _channelCount = 0;
+
   /// Determines whether performance monitoring is enabled or disabled.
   ///
   /// True if performance monitoring is enabled and false if performance
   /// monitoring is disabled. This is for dynamic enable/disable state. This
   /// does not reflect whether instrumentation is enabled/disabled.
-  Future<bool> isPerformanceCollectionEnabled() async {
-    final bool isEnabled = await channel
-        // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-        // https://github.com/flutter/flutter/issues/26431
-        // ignore: strong_mode_implicit_dynamic_method
-        .invokeMethod('FirebasePerformance#isPerformanceCollectionEnabled');
-    return isEnabled;
+  Future<bool> isPerformanceCollectionEnabled() {
+    return channel.invokeMethod<bool>(
+      'FirebasePerformance#isPerformanceCollectionEnabled',
+    );
   }
 
-  /// Enables or disables performance monitoring.
+  /// Enables or disables performance monitoring asynchronously.
   ///
   /// This setting is persisted and applied on future invocations of your
   /// application. By default, performance monitoring is enabled.
   Future<void> setPerformanceCollectionEnabled(bool enable) async {
-    // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-    // https://github.com/flutter/flutter/issues/26431
-    // ignore: strong_mode_implicit_dynamic_method
-    await channel.invokeMethod(
-        'FirebasePerformance#setPerformanceCollectionEnabled', enable);
+    return channel.invokeMethod<void>(
+      'FirebasePerformance#setPerformanceCollectionEnabled',
+      enable,
+    );
   }
 
   /// Creates a [Trace] object with given [name].
@@ -55,22 +50,33 @@ class FirebasePerformance {
   /// underscore _ character, max length of [Trace.maxTraceNameLength]
   /// characters.
   Trace newTrace(String name) {
-    return Trace._(_traceCount++, name);
+    final String channelName =
+        '${FirebasePerformance.channel.name}/$Trace/${_channelCount++}';
+
+    FirebasePerformance.channel.invokeMethod<void>(
+      '$FirebasePerformance#newTrace',
+      <String, dynamic>{'channelName': channelName, 'traceName': name},
+    );
+
+    final MethodChannel channel = MethodChannel(channelName);
+    return Trace._(channel);
   }
 
   /// Creates [HttpMetric] for collecting performance for one request/response.
   HttpMetric newHttpMetric(String url, HttpMethod httpMethod) {
-    return HttpMetric._(_httpMetricCount++, url, httpMethod);
-  }
+    final String channelName =
+        '${FirebasePerformance.channel.name}/$HttpMetric/${_channelCount++}';
 
-  /// Creates a [Trace] object with given [name] and start the trace.
-  ///
-  /// The [name] requires no leading or trailing whitespace, no leading
-  /// underscore _ character, max length of [Trace.maxTraceNameLength]
-  /// characters.
-  static Future<Trace> startTrace(String name) async {
-    final Trace trace = instance.newTrace(name);
-    await trace.start();
-    return trace;
+    FirebasePerformance.channel.invokeMethod<void>(
+      '$FirebasePerformance#newHttpMetric',
+      <String, dynamic>{
+        'channelName': channelName,
+        'url': url,
+        'httpMethod': httpMethod.toString(),
+      },
+    );
+
+    final MethodChannel channel = MethodChannel(channelName);
+    return HttpMetric._(channel);
   }
 }
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index a2e221b368e1..7ee889c21742 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -16,14 +16,9 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class HttpMetric extends PerformanceAttributes {
-  HttpMetric._(this._handle, this._url, this._httpMethod);
+  HttpMetric._(this._channel);
 
-  final int _handle;
-  final String _url;
-  final HttpMethod _httpMethod;
-
-  bool _hasStarted = false;
-  bool _hasStopped = false;
+  final MethodChannel _channel;
 
   /// HttpResponse code of the request.
   int httpResponseCode;
@@ -37,75 +32,33 @@ class HttpMetric extends PerformanceAttributes {
   /// Size of the response payload.
   int responsePayloadSize;
 
-  /// Starts this httpmetric.
-  ///
-  /// Can only be called once, otherwise assertion error is thrown.
+  @override
+  MethodChannel get _methodChannel => null;
+
+  /// Starts this [HttpMetric] asynchronously.
   ///
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    assert(!_hasStarted);
-
-    _hasStarted = true;
-    return FirebasePerformance.channel
-        // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-        // https://github.com/flutter/flutter/issues/26431
-        // ignore: strong_mode_implicit_dynamic_method
-        .invokeMethod('HttpMetric#start', <String, dynamic>{
-      'handle': _handle,
-      'url': _url,
-      'httpMethod': _httpMethod.index,
-    });
+    return _channel.invokeMethod<void>('$Trace#start');
   }
 
   /// Stops this httpMetric.
   ///
-  /// Can only be called once and only after start(), otherwise assertion error
-  /// is thrown. Data collected is automatically sent to the associated
-  /// Firebase console after stop() is called.
+  /// Can only be called once and only after start(), Data collected is
+  /// automatically sent to the associate Firebase console after stop() is
+  /// called. You can confirm that Performance Monitoring results appear in the
+  /// Firebase console. Results should appear within 12 hours.
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
-    assert(!_hasStopped);
-    assert(_hasStarted);
-
     final Map<String, dynamic> data = <String, dynamic>{
-      'handle': _handle,
       'httpResponseCode': httpResponseCode,
       'requestPayloadSize': requestPayloadSize,
       'responseContentType': responseContentType,
       'responsePayloadSize': responsePayloadSize,
-      'attributes': _attributes,
     };
 
-    _hasStopped = true;
-    // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-    // https://github.com/flutter/flutter/issues/26431
-    // ignore: strong_mode_implicit_dynamic_method
-    return FirebasePerformance.channel.invokeMethod('HttpMetric#stop', data);
-  }
-
-  /// Sets a String [value] for the specified [attribute].
-  ///
-  /// If the httpmetric has been stopped, this method throws an assertion
-  /// error.
-  ///
-  /// See [PerformanceAttributes.putAttribute].
-  @override
-  void putAttribute(String attribute, String value) {
-    assert(!_hasStopped);
-    super.putAttribute(attribute, value);
-  }
-
-  /// Removes an already added [attribute].
-  ///
-  /// If the httpmetric has been stopped, this method throws an assertion
-  /// error.
-  ///
-  /// See [PerformanceAttributes.removeAttribute].
-  @override
-  void removeAttribute(String attribute) {
-    assert(!_hasStopped);
-    super.removeAttribute(attribute);
+    return _channel.invokeMethod<void>('$Trace#stop', data);
   }
 }
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index 0543242fdeb2..87237e7cac34 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -4,10 +4,7 @@
 
 part of firebase_performance;
 
-/// Abstract class that allows adding/removing attributes to any object.
-///
-/// Enforces constraints for adding attributes and values required by
-/// FirebasePerformance API. See [putAttribute].
+/// Abstract class that allows adding/removing attributes to an object.
 abstract class PerformanceAttributes {
   /// Maximum allowed length of a key passed to [putAttribute].
   static const int maxAttributeKeyLength = 40;
@@ -18,10 +15,7 @@ abstract class PerformanceAttributes {
   /// Maximum allowed number of attributes that can be added.
   static const int maxCustomAttributes = 5;
 
-  final Map<String, String> _attributes = <String, String>{};
-
-  /// Copy of all the attributes added.
-  Map<String, String> get attributes => Map<String, String>.from(_attributes);
+  MethodChannel get _methodChannel;
 
   /// Sets a String [value] for the specified [attribute].
   ///
@@ -32,22 +26,25 @@ abstract class PerformanceAttributes {
   /// Name of the attribute has max length of [maxAttributeKeyLength]
   /// characters. Value of the attribute has max length of
   /// [maxAttributeValueLength] characters.
-  void putAttribute(String attribute, String value) {
-    assert(attribute != null);
-    assert(!attribute.startsWith(RegExp(r'[_\s]')));
-    assert(!attribute.contains(RegExp(r'[_\s]$')));
-    assert(attribute.length <= maxAttributeKeyLength);
-    assert(value.length <= maxAttributeValueLength);
-    assert(_attributes.length < maxCustomAttributes);
-
-    _attributes[attribute] = value;
+  Future<void> putAttribute(String attribute, String value) {
+    return _methodChannel.invokeMethod<void>(
+      'PerformanceAttributes#putAttribute',
+      <String, String>{'attribute': attribute, 'value': value},
+    );
   }
 
   /// Removes an already added [attribute].
-  void removeAttribute(String attribute) {
-    _attributes.remove(attribute);
+  Future<void> removeAttribute(String attribute) {
+    return _methodChannel.invokeMethod<void>(
+      'PerformanceAttributes#putAttribute',
+      attribute,
+    );
   }
 
-  /// Returns the value of an [attribute].
-  String getAttribute(String attribute) => _attributes[attribute];
+  /// All [attribute]s added.
+  Future<Map<String, String>> getAttributes() {
+    return _methodChannel.invokeMapMethod<String, String>(
+      'PerformanceAttributes#getAttributes',
+    );
+  }
 }
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 6ff6ab996ee9..3187115a26b3 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -19,111 +19,69 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class Trace extends PerformanceAttributes {
-  Trace._(this._handle, this._name) {
-    assert(_name != null);
-    assert(!_name.startsWith(RegExp(r'[_\s]')));
-    assert(!_name.contains(RegExp(r'[_\s]$')));
-    assert(_name.length <= maxTraceNameLength);
-  }
+  Trace._(this._channel);
 
   /// Maximum allowed length of the name of a [Trace].
   static const int maxTraceNameLength = 100;
 
-  final int _handle;
-  final String _name;
-
-  bool _hasStarted = false;
-  bool _hasStopped = false;
+  final MethodChannel _channel;
 
-  final HashMap<String, int> _counters = HashMap<String, int>();
+  @override
+  MethodChannel get _methodChannel => _channel;
 
-  /// Starts this trace.
+  /// Starts this [Trace] asynchronously.
   ///
-  /// Can only be called once, otherwise assertion error is thrown.
+  /// Can only be called once.
   ///
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    assert(!_hasStarted);
-
-    _hasStarted = true;
-    return FirebasePerformance.channel
-        // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-        // https://github.com/flutter/flutter/issues/26431
-        // ignore: strong_mode_implicit_dynamic_method
-        .invokeMethod('Trace#start', <String, dynamic>{
-      'handle': _handle,
-      'name': _name,
-    });
+    return _channel.invokeMethod<void>('$Trace#start');
   }
 
-  /// Stops this trace.
+  /// Stops this [Trace] asynchronously.
   ///
-  /// Can only be called once and only after start(), otherwise assertion error
-  /// is thrown. Data collected is automatically sent to the associated Firebase
-  /// console after stop() is called.
+  /// Can only be called once and only after start() Data collected is
+  /// automatically sent to the associated Firebase console after stop() is
+  /// called.
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
-    assert(!_hasStopped);
-    assert(_hasStarted);
-
-    final Map<String, dynamic> data = <String, dynamic>{
-      'handle': _handle,
-      'name': _name,
-      'counters': _counters,
-      'attributes': _attributes,
-    };
-
-    _hasStopped = true;
-    // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-    // https://github.com/flutter/flutter/issues/26431
-    // ignore: strong_mode_implicit_dynamic_method
-    return FirebasePerformance.channel.invokeMethod('Trace#stop', data);
+    return _channel.invokeMethod<void>('$Trace#stop');
   }
 
-  /// Increments the counter with the given [name] by [incrementBy].
+  /// Increments the metric with the given name asynchronously.
   ///
-  /// The counter is incremented by 1 if [incrementBy] was not passed. If a
-  /// counter does not already exist, a new one will be created. If the trace
-  /// has not been started or has already been stopped, an assertion error is
-  /// thrown.
-  ///
-  /// The name of the counter requires no leading or
-  /// trailing whitespace, no leading underscore _ character, and max length of
-  /// 32 characters.
-  void incrementCounter(String name, [int incrementBy = 1]) {
-    assert(!_hasStopped);
-    assert(name != null);
-    assert(!name.startsWith(RegExp(r'[_\s]')));
-    assert(!name.contains(RegExp(r'[_\s]$')));
-    assert(name.length <= 32);
-
-    _counters.putIfAbsent(name, () => 0);
-    _counters[name] += incrementBy;
+  /// If the metric does not exist, a new one will be created. If the trace has
+  /// not been started or has already been stopped, returns immediately without
+  /// taking action.
+  Future<void> incrementMetric(String name, int value) {
+    return _channel.invokeMethod<void>(
+      '$Trace#incrementMetric',
+      <String, dynamic>{'name': name, 'value': value},
+    );
   }
 
-  /// Sets a String [value] for the specified [attribute].
-  ///
-  /// If the trace has been stopped, this method throws an assertion
-  /// error.
+  /// Sets the value of the metric with the given name asynchronously.
   ///
-  /// See [PerformanceAttributes.putAttribute].
-  @override
-  void putAttribute(String attribute, String value) {
-    assert(!_hasStopped);
-    super.putAttribute(attribute, value);
+  /// If a metric with the given name doesn't exist, a new one will be created.
+  /// If the trace has not been started or has already been stopped, returns
+  /// immediately without taking action.
+  Future<void> putMetric(String name, int value) {
+    return _channel.invokeMethod<void>(
+      '$Trace#putMetric',
+      <String, dynamic>{'name': name, 'value': value},
+    );
   }
 
-  /// Removes an already added [attribute].
-  ///
-  /// If the trace has been stopped, this method throws an assertion
-  /// error.
+  /// Gets the value of the metric with the given name asynchronously.
   ///
-  /// See [PerformanceAttributes.removeAttribute].
-  @override
-  void removeAttribute(String attribute) {
-    assert(!_hasStopped);
-    super.removeAttribute(attribute);
+  /// If a metric with the given name doesn't exist, it is NOT created and a 0
+  /// is returned.
+  Future<int> getMetric(String name) {
+    return _channel.invokeMethod<int>(
+      '$Trace#getMetric',
+      <String, dynamic>{'name': name},
+    );
   }
 }

From b3d698cfda941c9c1e5e9de427a24d07ac03ffb0 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 22 Apr 2019 15:21:57 -0700
Subject: [PATCH 03/40] Undo changes

---
 packages/firebase_performance/lib/src/trace.dart | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 3187115a26b3..b4fc363bc1b6 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -9,7 +9,7 @@ part of firebase_performance;
 /// A trace is a report of performance data associated with some of the
 /// code in your app. You can have multiple custom traces, and it is
 /// possible to have more than one custom trace running at a time. Each custom
-/// trace can have multiple counters and attributes added to help measure
+/// trace can have multiple metrics and attributes added to help measure
 /// performance related events. A trace also measures the time between calling
 /// start() and stop().
 ///
@@ -74,7 +74,7 @@ class Trace extends PerformanceAttributes {
     );
   }
 
-  /// Gets the value of the metric with the given name asynchronously.
+  /// Gets the value of the metric with the given name.
   ///
   /// If a metric with the given name doesn't exist, it is NOT created and a 0
   /// is returned.

From cfa200cd3de8d4541a6901c6231a93ef2917d961 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 22 Apr 2019 15:27:03 -0700
Subject: [PATCH 04/40] Formatting and suppressing warnings

---
 .../flutter/plugins/firebaseperformance/FlutterHttpMetric.java | 3 ++-
 .../io/flutter/plugins/firebaseperformance/FlutterTrace.java   | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index 1d2e8a3729af..9f6c41f67a54 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -6,11 +6,12 @@
 
 import com.google.firebase.perf.FirebasePerformance;
 import com.google.firebase.perf.metrics.HttpMetric;
-import java.util.Map;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
+import java.util.Map;
 
+@SuppressWarnings("ConstantConditions")
 public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
   private final HttpMetric httpMetric;
 
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index 3ccbfdd07b14..7488204e8d11 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -6,11 +6,12 @@
 
 import com.google.firebase.perf.FirebasePerformance;
 import com.google.firebase.perf.metrics.Trace;
-import java.util.Map;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
+import java.util.Map;
 
+@SuppressWarnings("ConstantConditions")
 public class FlutterTrace implements MethodChannel.MethodCallHandler {
   private final Trace trace;
 

From e3aa0e91b578590d34f5b496dc06665b53bbef6c Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 12:00:56 -0700
Subject: [PATCH 05/40] Update metric take individual parameters

---
 .../FlutterFirebasePerformance.java           | 20 ++---
 .../FlutterHttpMetric.java                    | 85 ++++++++++---------
 .../firebaseperformance/FlutterTrace.java     | 63 +++++---------
 3 files changed, 79 insertions(+), 89 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
index bc3da7ea53f9..9e66cf732f50 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
@@ -1,4 +1,4 @@
-// Copyright 2018 The Chromium Authors. All rights reserved.
+// Copyright 2019 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -29,13 +29,13 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
         isPerformanceCollectionEnabled(result);
         break;
       case "FirebasePerformance#setPerformanceCollectionEnabled":
-        setPerformanceCollectionEnabled(call.arguments, result);
+        setPerformanceCollectionEnabled(call, result);
         break;
       case "FirebasePerformance#newTrace":
-        newTrace(call.arguments, result);
+        newTrace(call, result);
         break;
       case "FirebasePerformance#newHttpMetric":
-        newHttpMetric(call.arguments, result);
+        newHttpMetric(call, result);
         break;
       default:
         result.notImplemented();
@@ -46,17 +46,17 @@ private void isPerformanceCollectionEnabled(MethodChannel.Result result) {
     result.success(performance.isPerformanceCollectionEnabled());
   }
 
-  private void setPerformanceCollectionEnabled(Object arguments, MethodChannel.Result result) {
-    final boolean enabled = (Boolean) arguments;
+  private void setPerformanceCollectionEnabled(MethodCall call, MethodChannel.Result result) {
+    final boolean enabled = (Boolean) call.arguments;
     performance.setPerformanceCollectionEnabled(enabled);
     result.success(null);
   }
 
-  private void newTrace(Object arguments, MethodChannel.Result result) {
-    new FlutterTrace(performance, binaryMessenger, arguments, result);
+  private void newTrace(MethodCall call, MethodChannel.Result result) {
+    new FlutterTrace(performance, binaryMessenger, call, result);
   }
 
-  private void newHttpMetric(Object arguments, MethodChannel.Result result) {
-    new FlutterHttpMetric(performance, binaryMessenger, arguments, result);
+  private void newHttpMetric(MethodCall call, MethodChannel.Result result) {
+    new FlutterHttpMetric(performance, binaryMessenger, call, result);
   }
 }
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index 9f6c41f67a54..2ef6163bc620 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -1,4 +1,4 @@
-// Copyright 2018 The Chromium Authors. All rights reserved.
+// Copyright 2019 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -9,7 +9,6 @@
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
-import java.util.Map;
 
 @SuppressWarnings("ConstantConditions")
 public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
@@ -18,14 +17,11 @@ public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
   FlutterHttpMetric(
       FirebasePerformance performance,
       BinaryMessenger messenger,
-      Object arguments,
+      MethodCall call,
       MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String channelName = (String) args.get("channelName");
-    final String url = (String) args.get("url");
-    final String httpMethod = (String) args.get("httpMethod");
+    final String channelName = call.argument("channelName");
+    final String url = call.argument("url");
+    final String httpMethod = call.argument("httpMethod");
 
     this.httpMetric = performance.newHttpMetric(url, httpMethod);
 
@@ -42,13 +38,25 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
         start(result);
         break;
       case "HttpMetric#stop":
-        stop(call.arguments, result);
+        stop(result);
+        break;
+      case "HttpMetric#httpResponseCode":
+        setHttpResponseCode(call, result);
+        break;
+      case "HttpMetric#requestPayloadSize":
+        setRequestPayloadSize(call, result);
+        break;
+      case "HttpMetric#responseContentType":
+        setResponseContentType(call, result);
+        break;
+      case "HttpMetric#responsePayloadSize":
+        setResponsePayloadSize(call, result);
         break;
       case "PerformanceAttributes#putAttribute":
-        putAttribute(call.arguments, result);
+        putAttribute(call, result);
         break;
       case "PerformanceAttributes#removeAttribute":
-        removeAttribute(call.arguments, result);
+        removeAttribute(call, result);
         break;
       case "PerformanceAttributes#getAttributes":
         getAttributes(result);
@@ -63,46 +71,47 @@ private void start(MethodChannel.Result result) {
     result.success(null);
   }
 
-  private void stop(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
+  private void stop(MethodChannel.Result result) {
+    httpMetric.stop();
+    result.success(null);
+  }
 
-    final Integer httpResponseCode = (Integer) args.get("httpResponseCode");
-    final Number requestPayloadSize = (Number) args.get("requestPayloadSize");
-    final String responseContentType = (String) args.get("responseContentType");
-    final Number responsePayloadSize = (Number) args.get("responsePayloadSize");
+  private void setHttpResponseCode(MethodCall call, MethodChannel.Result result) {
+    final Integer httpResponseCode = call.argument("httpResponseCode");
+    httpMetric.setHttpResponseCode(httpResponseCode);
+    result.success(null);
+  }
 
-    if (requestPayloadSize != null) {
-      httpMetric.setRequestPayloadSize(requestPayloadSize.longValue());
-    }
-    if (responsePayloadSize != null) {
-      httpMetric.setResponsePayloadSize(responsePayloadSize.longValue());
-    }
+  private void setRequestPayloadSize(MethodCall call, MethodChannel.Result result) {
+    final Number payloadSize = call.argument("requestPayloadSize");
+    httpMetric.setRequestPayloadSize(payloadSize.longValue());
+    result.success(null);
+  }
 
-    if (httpResponseCode != null) httpMetric.setHttpResponseCode(httpResponseCode);
-    if (responseContentType != null) httpMetric.setResponseContentType(responseContentType);
+  private void setResponseContentType(MethodCall call, MethodChannel.Result result) {
+    final String contentType = call.argument("responseContentType");
+    httpMetric.setResponseContentType(contentType);
+    result.success(null);
+  }
 
-    httpMetric.stop();
+  private void setResponsePayloadSize(MethodCall call, MethodChannel.Result result) {
+    final Number payloadSize = call.argument("responsePayloadSize");
+    httpMetric.setResponsePayloadSize(payloadSize.longValue());
     result.success(null);
   }
 
-  private void putAttribute(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
 
-    final String attribute = (String) args.get("attribute");
-    final String value = (String) args.get("value");
+  private void putAttribute(MethodCall call, MethodChannel.Result result) {
+    final String attribute = call.argument("attribute");
+    final String value = call.argument("value");
 
     httpMetric.putAttribute(attribute, value);
 
     result.success(null);
   }
 
-  private void removeAttribute(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String attribute = (String) args.get("attribute");
+  private void removeAttribute(MethodCall call, MethodChannel.Result result) {
+    final String attribute = call.argument("attribute");
     httpMetric.removeAttribute(attribute);
 
     result.success(null);
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index 7488204e8d11..566e99c5d179 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -1,4 +1,4 @@
-// Copyright 2018 The Chromium Authors. All rights reserved.
+// Copyright 2019 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -9,7 +9,6 @@
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
-import java.util.Map;
 
 @SuppressWarnings("ConstantConditions")
 public class FlutterTrace implements MethodChannel.MethodCallHandler {
@@ -18,13 +17,10 @@ public class FlutterTrace implements MethodChannel.MethodCallHandler {
   FlutterTrace(
       FirebasePerformance performance,
       BinaryMessenger messenger,
-      Object arguments,
+      MethodCall call,
       MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String traceName = (String) args.get("traceName");
-    final String channelName = (String) args.get("channelName");
+    final String traceName = call.argument("traceName");
+    final String channelName = call.argument("channelName");
 
     this.trace = performance.newTrace(traceName);
 
@@ -44,19 +40,19 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
         stop(result);
         break;
       case "Trace#putMetric":
-        putMetric(call.arguments, result);
+        putMetric(call, result);
         break;
       case "Trace#incrementMetric":
-        incrementMetric(call.arguments, result);
+        incrementMetric(call, result);
         break;
       case "Trace#getMetric":
-        getMetric(call.arguments, result);
+        getMetric(call, result);
         break;
       case "PerformanceAttributes#putAttribute":
-        putAttribute(call.arguments, result);
+        putAttribute(call, result);
         break;
       case "PerformanceAttributes#removeAttribute":
-        removeAttribute(call.arguments, result);
+        removeAttribute(call, result);
         break;
       case "PerformanceAttributes#getAttributes":
         getAttributes(result);
@@ -76,54 +72,39 @@ private void stop(MethodChannel.Result result) {
     result.success(null);
   }
 
-  private void putMetric(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String name = (String) args.get("name");
-    final Number value = (Number) args.get("value");
+  private void putMetric(MethodCall call, MethodChannel.Result result) {
+    final String name = call.argument("name");
+    final Number value = call.argument("value");
     trace.putMetric(name, value.longValue());
 
     result.success(null);
   }
 
-  private void incrementMetric(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String name = (String) args.get("name");
-    final Number value = (Number) args.get("value");
+  private void incrementMetric(MethodCall call, MethodChannel.Result result) {
+    final String name = call.argument("name");
+    final Number value = call.argument("value");
     trace.incrementMetric(name, value.longValue());
 
     result.success(null);
   }
 
-  private void getMetric(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String name = (String) args.get("name");
+  private void getMetric(MethodCall call, MethodChannel.Result result) {
+    final String name = call.argument("name");
 
     result.success(trace.getLongMetric(name));
   }
 
-  private void putAttribute(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String attribute = (String) args.get("attribute");
-    final String value = (String) args.get("value");
+  private void putAttribute(MethodCall call, MethodChannel.Result result) {
+    final String attribute = call.argument("attribute");
+    final String value = call.argument("value");
 
     trace.putAttribute(attribute, value);
 
     result.success(null);
   }
 
-  private void removeAttribute(Object arguments, MethodChannel.Result result) {
-    @SuppressWarnings("unchecked")
-    final Map<String, Object> args = (Map<String, Object>) arguments;
-
-    final String attribute = (String) args.get("attribute");
+  private void removeAttribute(MethodCall call, MethodChannel.Result result) {
+    final String attribute = call.argument("attribute");
     trace.removeAttribute(attribute);
 
     result.success(null);

From db5acb6432f29f2a88b8c48dbf06ac797f425858 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 12:19:08 -0700
Subject: [PATCH 06/40] Update HttpMetric

---
 .../lib/src/firebase_performance.dart         |  2 +-
 .../lib/src/http_metric.dart                  | 51 ++++++++++++-------
 .../lib/src/performance_attributes.dart       |  6 +--
 .../firebase_performance/lib/src/trace.dart   |  5 +-
 4 files changed, 39 insertions(+), 25 deletions(-)

diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index 165ed0851f87..f1640665ca64 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -47,7 +47,7 @@ class FirebasePerformance {
   /// Creates a [Trace] object with given [name].
   ///
   /// The [name] requires no leading or trailing whitespace, no leading
-  /// underscore _ character, max length of [Trace.maxTraceNameLength]
+  /// underscore _ character, and max length of [Trace.maxTraceNameLength]
   /// characters.
   Trace newTrace(String name) {
     final String channelName =
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index 7ee889c21742..eb614139cd17 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -6,9 +6,9 @@ part of firebase_performance;
 
 /// Metric used to collect data for network requests/responses.
 ///
-/// It is possible to have more than one httpmetric running at a time.
+/// It is possible to have more than one [HttpMetric] running at a time.
 /// Attributes can also be added to help measure performance related events. A
-/// httpmetric also measures the time between calling start() and stop().
+/// [HttpMetric] also measures the time between calling start() and stop().
 ///
 /// Data collected is automatically sent to the associated Firebase console
 /// after stop() is called.
@@ -20,30 +20,50 @@ class HttpMetric extends PerformanceAttributes {
 
   final MethodChannel _channel;
 
+  @override
+  MethodChannel get _methodChannel => _channel;
+
   /// HttpResponse code of the request.
-  int httpResponseCode;
+  set httpResponseCode(int httpResponseCode) {
+    _channel.invokeMethod<void>(
+      '$HttpMetric#httpResponseCode',
+      httpResponseCode,
+    );
+  }
 
   /// Size of the request payload.
-  int requestPayloadSize;
+  set requestPayloadSize(int requestPayloadSize) {
+    _channel.invokeMethod<void>(
+      '$HttpMetric#requestPayloadSize',
+      requestPayloadSize,
+    );
+  }
 
   /// Content type of the response such as text/html, application/json, etc...
-  String responseContentType;
+  set responseContentType(String responseContentType) {
+    _channel.invokeMethod<void>(
+      '$HttpMetric#responseContentType',
+      responseContentType,
+    );
+  }
 
   /// Size of the response payload.
-  int responsePayloadSize;
-
-  @override
-  MethodChannel get _methodChannel => null;
+  set responsePayloadSize(int responsePayloadSize) {
+    _channel.invokeMethod<void>(
+      '$HttpMetric#responsePayloadSize',
+      responsePayloadSize,
+    );
+  }
 
   /// Starts this [HttpMetric] asynchronously.
   ///
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    return _channel.invokeMethod<void>('$Trace#start');
+    return _channel.invokeMethod<void>('$HttpMetric#start');
   }
 
-  /// Stops this httpMetric.
+  /// Stops this [HttpMetric].
   ///
   /// Can only be called once and only after start(), Data collected is
   /// automatically sent to the associate Firebase console after stop() is
@@ -52,13 +72,6 @@ class HttpMetric extends PerformanceAttributes {
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
-    final Map<String, dynamic> data = <String, dynamic>{
-      'httpResponseCode': httpResponseCode,
-      'requestPayloadSize': requestPayloadSize,
-      'responseContentType': responseContentType,
-      'responsePayloadSize': responsePayloadSize,
-    };
-
-    return _channel.invokeMethod<void>('$Trace#stop', data);
+    return _channel.invokeMethod<void>('$HttpMetric#stop');
   }
 }
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index 87237e7cac34..b9247e73b1b0 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -28,7 +28,7 @@ abstract class PerformanceAttributes {
   /// [maxAttributeValueLength] characters.
   Future<void> putAttribute(String attribute, String value) {
     return _methodChannel.invokeMethod<void>(
-      'PerformanceAttributes#putAttribute',
+      '$PerformanceAttributes#putAttribute',
       <String, String>{'attribute': attribute, 'value': value},
     );
   }
@@ -36,7 +36,7 @@ abstract class PerformanceAttributes {
   /// Removes an already added [attribute].
   Future<void> removeAttribute(String attribute) {
     return _methodChannel.invokeMethod<void>(
-      'PerformanceAttributes#putAttribute',
+      '$PerformanceAttributes#putAttribute',
       attribute,
     );
   }
@@ -44,7 +44,7 @@ abstract class PerformanceAttributes {
   /// All [attribute]s added.
   Future<Map<String, String>> getAttributes() {
     return _methodChannel.invokeMapMethod<String, String>(
-      'PerformanceAttributes#getAttributes',
+      '$PerformanceAttributes#getAttributes',
     );
   }
 }
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index b4fc363bc1b6..5298ea5dde06 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -4,7 +4,7 @@
 
 part of firebase_performance;
 
-/// Trace allows you to set the beginning and end of a custom trace in your app.
+/// [Trace] allows you to set the beginning and end of a custom trace in your app.
 ///
 /// A trace is a report of performance data associated with some of the
 /// code in your app. You can have multiple custom traces, and it is
@@ -43,7 +43,8 @@ class Trace extends PerformanceAttributes {
   ///
   /// Can only be called once and only after start() Data collected is
   /// automatically sent to the associated Firebase console after stop() is
-  /// called.
+  /// called. You can confirm that Performance Monitoring results appear in the
+  /// Firebase console. Results should appear within 12 hours.
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {

From 588c7fb01a19b988cc5209f04486f5b4291d99c1 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 12:41:19 -0700
Subject: [PATCH 07/40] Unregister MethodCallHandler

---
 .../plugins/firebaseperformance/FlutterHttpMetric.java        | 4 +++-
 .../io/flutter/plugins/firebaseperformance/FlutterTrace.java  | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index 2ef6163bc620..0a71239b89fc 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -13,6 +13,7 @@
 @SuppressWarnings("ConstantConditions")
 public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
   private final HttpMetric httpMetric;
+  private final MethodChannel channel;
 
   FlutterHttpMetric(
       FirebasePerformance performance,
@@ -25,7 +26,7 @@ public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
 
     this.httpMetric = performance.newHttpMetric(url, httpMethod);
 
-    final MethodChannel channel = new MethodChannel(messenger, channelName);
+    this.channel = new MethodChannel(messenger, channelName);
     channel.setMethodCallHandler(this);
 
     result.success(null);
@@ -73,6 +74,7 @@ private void start(MethodChannel.Result result) {
 
   private void stop(MethodChannel.Result result) {
     httpMetric.stop();
+    channel.setMethodCallHandler(null);
     result.success(null);
   }
 
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index 566e99c5d179..9b3b4c8f58e2 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -13,6 +13,7 @@
 @SuppressWarnings("ConstantConditions")
 public class FlutterTrace implements MethodChannel.MethodCallHandler {
   private final Trace trace;
+  private final MethodChannel channel;
 
   FlutterTrace(
       FirebasePerformance performance,
@@ -24,7 +25,7 @@ public class FlutterTrace implements MethodChannel.MethodCallHandler {
 
     this.trace = performance.newTrace(traceName);
 
-    final MethodChannel channel = new MethodChannel(messenger, channelName);
+    this.channel = new MethodChannel(messenger, channelName);
     channel.setMethodCallHandler(this);
 
     result.success(null);
@@ -69,6 +70,7 @@ private void start(MethodChannel.Result result) {
 
   private void stop(MethodChannel.Result result) {
     trace.stop();
+    channel.setMethodCallHandler(null);
     result.success(null);
   }
 

From 55d69991a55e53446d3352e9f76e78a5e2c6ac39 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 12:52:06 -0700
Subject: [PATCH 08/40] Parse HttpMethod

---
 .../FlutterHttpMetric.java                    | 27 ++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index 0a71239b89fc..d3073f37b52f 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -12,6 +12,31 @@
 
 @SuppressWarnings("ConstantConditions")
 public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
+  private static String parseHttpMethod(String httpMethod) {
+    switch (httpMethod) {
+      case "HttpMethod.Connect":
+        return FirebasePerformance.HttpMethod.CONNECT;
+      case "HttpMethod.Delete":
+        return FirebasePerformance.HttpMethod.DELETE;
+      case "HttpMethod.Get":
+        return FirebasePerformance.HttpMethod.GET;
+      case "HttpMethod.Head":
+        return FirebasePerformance.HttpMethod.HEAD;
+      case "HttpMethod.Options":
+        return FirebasePerformance.HttpMethod.OPTIONS;
+      case "HttpMethod.Patch":
+        return FirebasePerformance.HttpMethod.PATCH;
+      case "HttpMethod.Post":
+        return FirebasePerformance.HttpMethod.POST;
+      case "HttpMethod.Put":
+        return FirebasePerformance.HttpMethod.PUT;
+      case "HttpMethod.Trace":
+        return FirebasePerformance.HttpMethod.TRACE;
+      default:
+        throw new IllegalArgumentException(String.format("No HttpMethod for: %s", httpMethod));
+    }
+  }
+
   private final HttpMetric httpMetric;
   private final MethodChannel channel;
 
@@ -24,7 +49,7 @@ public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
     final String url = call.argument("url");
     final String httpMethod = call.argument("httpMethod");
 
-    this.httpMetric = performance.newHttpMetric(url, httpMethod);
+    this.httpMetric = performance.newHttpMetric(url, parseHttpMethod(httpMethod));
 
     this.channel = new MethodChannel(messenger, channelName);
     channel.setMethodCallHandler(this);

From 236da2c737cb5e903c2dfb1780fe557c7f44c623 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 13:37:14 -0700
Subject: [PATCH 09/40] Fix MethodChannel Unit tests

---
 .../lib/src/http_metric.dart                  |  19 +-
 .../lib/src/performance_attributes.dart       |  11 +-
 .../firebase_performance/lib/src/trace.dart   |  17 +-
 .../test/firebase_performance_test.dart       | 359 +++++++-----------
 4 files changed, 165 insertions(+), 241 deletions(-)

diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index eb614139cd17..aeabb8024c95 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -16,16 +16,17 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class HttpMetric extends PerformanceAttributes {
-  HttpMetric._(this._channel);
+  HttpMetric._(this.channel);
 
-  final MethodChannel _channel;
+  @visibleForTesting
+  final MethodChannel channel;
 
   @override
-  MethodChannel get _methodChannel => _channel;
+  MethodChannel get methodChannel => channel;
 
   /// HttpResponse code of the request.
   set httpResponseCode(int httpResponseCode) {
-    _channel.invokeMethod<void>(
+    channel.invokeMethod<void>(
       '$HttpMetric#httpResponseCode',
       httpResponseCode,
     );
@@ -33,7 +34,7 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Size of the request payload.
   set requestPayloadSize(int requestPayloadSize) {
-    _channel.invokeMethod<void>(
+    channel.invokeMethod<void>(
       '$HttpMetric#requestPayloadSize',
       requestPayloadSize,
     );
@@ -41,7 +42,7 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Content type of the response such as text/html, application/json, etc...
   set responseContentType(String responseContentType) {
-    _channel.invokeMethod<void>(
+    channel.invokeMethod<void>(
       '$HttpMetric#responseContentType',
       responseContentType,
     );
@@ -49,7 +50,7 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Size of the response payload.
   set responsePayloadSize(int responsePayloadSize) {
-    _channel.invokeMethod<void>(
+    channel.invokeMethod<void>(
       '$HttpMetric#responsePayloadSize',
       responsePayloadSize,
     );
@@ -60,7 +61,7 @@ class HttpMetric extends PerformanceAttributes {
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    return _channel.invokeMethod<void>('$HttpMetric#start');
+    return channel.invokeMethod<void>('$HttpMetric#start');
   }
 
   /// Stops this [HttpMetric].
@@ -72,6 +73,6 @@ class HttpMetric extends PerformanceAttributes {
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
-    return _channel.invokeMethod<void>('$HttpMetric#stop');
+    return channel.invokeMethod<void>('$HttpMetric#stop');
   }
 }
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index b9247e73b1b0..b74869e11878 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -15,7 +15,8 @@ abstract class PerformanceAttributes {
   /// Maximum allowed number of attributes that can be added.
   static const int maxCustomAttributes = 5;
 
-  MethodChannel get _methodChannel;
+  @visibleForTesting
+  MethodChannel get methodChannel;
 
   /// Sets a String [value] for the specified [attribute].
   ///
@@ -27,7 +28,7 @@ abstract class PerformanceAttributes {
   /// characters. Value of the attribute has max length of
   /// [maxAttributeValueLength] characters.
   Future<void> putAttribute(String attribute, String value) {
-    return _methodChannel.invokeMethod<void>(
+    return methodChannel.invokeMethod<void>(
       '$PerformanceAttributes#putAttribute',
       <String, String>{'attribute': attribute, 'value': value},
     );
@@ -35,15 +36,15 @@ abstract class PerformanceAttributes {
 
   /// Removes an already added [attribute].
   Future<void> removeAttribute(String attribute) {
-    return _methodChannel.invokeMethod<void>(
-      '$PerformanceAttributes#putAttribute',
+    return methodChannel.invokeMethod<void>(
+      '$PerformanceAttributes#removeAttribute',
       attribute,
     );
   }
 
   /// All [attribute]s added.
   Future<Map<String, String>> getAttributes() {
-    return _methodChannel.invokeMapMethod<String, String>(
+    return methodChannel.invokeMapMethod<String, String>(
       '$PerformanceAttributes#getAttributes',
     );
   }
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 5298ea5dde06..cda5c066fecc 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -19,15 +19,16 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class Trace extends PerformanceAttributes {
-  Trace._(this._channel);
+  Trace._(this.channel);
 
   /// Maximum allowed length of the name of a [Trace].
   static const int maxTraceNameLength = 100;
 
-  final MethodChannel _channel;
+  @visibleForTesting
+  final MethodChannel channel;
 
   @override
-  MethodChannel get _methodChannel => _channel;
+  MethodChannel get methodChannel => channel;
 
   /// Starts this [Trace] asynchronously.
   ///
@@ -36,7 +37,7 @@ class Trace extends PerformanceAttributes {
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    return _channel.invokeMethod<void>('$Trace#start');
+    return channel.invokeMethod<void>('$Trace#start');
   }
 
   /// Stops this [Trace] asynchronously.
@@ -48,7 +49,7 @@ class Trace extends PerformanceAttributes {
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
-    return _channel.invokeMethod<void>('$Trace#stop');
+    return channel.invokeMethod<void>('$Trace#stop');
   }
 
   /// Increments the metric with the given name asynchronously.
@@ -57,7 +58,7 @@ class Trace extends PerformanceAttributes {
   /// not been started or has already been stopped, returns immediately without
   /// taking action.
   Future<void> incrementMetric(String name, int value) {
-    return _channel.invokeMethod<void>(
+    return channel.invokeMethod<void>(
       '$Trace#incrementMetric',
       <String, dynamic>{'name': name, 'value': value},
     );
@@ -69,7 +70,7 @@ class Trace extends PerformanceAttributes {
   /// If the trace has not been started or has already been stopped, returns
   /// immediately without taking action.
   Future<void> putMetric(String name, int value) {
-    return _channel.invokeMethod<void>(
+    return channel.invokeMethod<void>(
       '$Trace#putMetric',
       <String, dynamic>{'name': name, 'value': value},
     );
@@ -80,7 +81,7 @@ class Trace extends PerformanceAttributes {
   /// If a metric with the given name doesn't exist, it is NOT created and a 0
   /// is returned.
   Future<int> getMetric(String name) {
-    return _channel.invokeMethod<int>(
+    return channel.invokeMethod<int>(
       '$Trace#getMetric',
       <String, dynamic>{'name': name},
     );
diff --git a/packages/firebase_performance/test/firebase_performance_test.dart b/packages/firebase_performance/test/firebase_performance_test.dart
index bf2b42e50499..cf45623f5f41 100644
--- a/packages/firebase_performance/test/firebase_performance_test.dart
+++ b/packages/firebase_performance/test/firebase_performance_test.dart
@@ -7,15 +7,10 @@ import 'package:flutter/services.dart';
 import 'package:firebase_performance/firebase_performance.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-class MockPerformanceAttributes extends PerformanceAttributes {}
-
 void main() {
   group('$FirebasePerformance', () {
     final FirebasePerformance performance = FirebasePerformance.instance;
     final List<MethodCall> log = <MethodCall>[];
-    bool performanceCollectionEnable = true;
-    int currentTraceHandle;
-    int currentHttpMetricHandle;
 
     setUp(() {
       FirebasePerformance.channel
@@ -23,20 +18,7 @@ void main() {
         log.add(methodCall);
         switch (methodCall.method) {
           case 'FirebasePerformance#isPerformanceCollectionEnabled':
-            return performanceCollectionEnable;
-          case 'FirebasePerformance#setPerformanceCollectionEnabled':
-            performanceCollectionEnable = methodCall.arguments;
-            return null;
-          case 'Trace#start':
-            currentTraceHandle = methodCall.arguments['handle'];
-            return null;
-          case 'Trace#stop':
-            return null;
-          case 'HttpMetric#start':
-            currentHttpMetricHandle = methodCall.arguments['handle'];
-            return null;
-          case 'HttpMetric#stop':
-            return null;
+            return true;
           default:
             return null;
         }
@@ -47,7 +29,7 @@ void main() {
     test('isPerformanceCollectionEnabled', () async {
       final bool enabled = await performance.isPerformanceCollectionEnabled();
 
-      expect(performanceCollectionEnable, enabled);
+      expect(enabled, isTrue);
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#isPerformanceCollectionEnabled',
@@ -58,10 +40,7 @@ void main() {
 
     test('setPerformanceCollectionEnabled', () async {
       await performance.setPerformanceCollectionEnabled(true);
-      performanceCollectionEnable = true;
-
       await performance.setPerformanceCollectionEnabled(false);
-      performanceCollectionEnable = false;
 
       expect(log, <Matcher>[
         isMethodCall(
@@ -77,188 +56,121 @@ void main() {
 
     test('newTrace', () async {
       final Trace trace = performance.newTrace('test-trace');
-      await trace.start();
+
+      await pumpEventQueue();
 
       expect(log, <Matcher>[
         isMethodCall(
-          'Trace#start',
-          arguments: <String, Object>{
-            'handle': currentTraceHandle,
-            'name': 'test-trace',
+          'FirebasePerformance#newTrace',
+          arguments: <String, dynamic>{
+            'channelName': trace.channel.name,
+            'traceName': 'test-trace',
           },
         ),
       ]);
     });
 
     test('newHttpMetric', () async {
+      final String url = 'https://google.com';
+
       final HttpMetric metric = performance.newHttpMetric(
-        'https://google.com',
+        url,
         HttpMethod.Connect,
       );
-      await metric.start();
 
-      expect(log, <Matcher>[
-        isMethodCall(
-          'HttpMetric#start',
-          arguments: <String, Object>{
-            'handle': currentTraceHandle,
-            'url': 'https://google.com',
-            'httpMethod': HttpMethod.Connect.index,
-          },
-        ),
-      ]);
-    });
-
-    test('startTrace', () async {
-      await FirebasePerformance.startTrace('startTrace-test');
+      await pumpEventQueue();
 
       expect(log, <Matcher>[
         isMethodCall(
-          'Trace#start',
-          arguments: <String, Object>{
-            'handle': currentTraceHandle,
-            'name': 'startTrace-test',
+          'FirebasePerformance#newHttpMetric',
+          arguments: <String, dynamic>{
+            'channelName': metric.channel.name,
+            'url': url,
+            'httpMethod': HttpMethod.Connect.toString(),
           },
         ),
       ]);
     });
 
     test('$HttpMethod', () async {
-      expect(HttpMethod.Connect.index, 0);
-      expect(HttpMethod.Delete.index, 1);
-      expect(HttpMethod.Get.index, 2);
-      expect(HttpMethod.Head.index, 3);
-      expect(HttpMethod.Options.index, 4);
-      expect(HttpMethod.Patch.index, 5);
-      expect(HttpMethod.Post.index, 6);
-      expect(HttpMethod.Put.index, 7);
-      expect(HttpMethod.Trace.index, 8);
+      final String url = 'https://google.com';
+
+      for (HttpMethod method in HttpMethod.values) {
+        final HttpMetric metric = performance.newHttpMetric(
+          'https://google.com',
+          method,
+        );
+
+        await pumpEventQueue();
+
+        expect(log, <Matcher>[
+          isMethodCall(
+            'FirebasePerformance#newHttpMetric',
+            arguments: <String, dynamic>{
+              'channelName': metric.channel.name,
+              'url': url,
+              'httpMethod': method.toString(),
+            },
+          ),
+        ]);
+
+        log.clear();
+      }
     });
 
     group('$Trace', () {
       Trace testTrace;
+      final List<MethodCall> traceLog = <MethodCall>[];
 
       setUp(() {
         testTrace = performance.newTrace('test');
+        testTrace.channel
+            .setMockMethodCallHandler((MethodCall methodCall) async {
+          traceLog.add(methodCall);
+          switch (methodCall.method) {
+            case 'FirebasePerformance#isPerformanceCollectionEnabled':
+              return true;
+            default:
+              return null;
+          }
+        });
+        traceLog.clear();
       });
 
       test('start', () async {
+        await pumpEventQueue();
+
         await testTrace.start();
 
-        expect(log, <Matcher>[
-          isMethodCall(
-            'Trace#start',
-            arguments: <String, Object>{
-              'handle': currentTraceHandle,
-              'name': 'test',
-            },
-          ),
+        expect(traceLog, <Matcher>[
+          isMethodCall('Trace#start', arguments: null),
         ]);
       });
 
       test('stop', () async {
-        await testTrace.start();
+        await pumpEventQueue();
+
         await testTrace.stop();
 
-        expect(log, <Matcher>[
-          isMethodCall('Trace#start', arguments: <String, Object>{
-            'handle': currentTraceHandle,
-            'name': 'test',
-          }),
-          isMethodCall(
-            'Trace#stop',
-            arguments: <String, dynamic>{
-              'handle': currentTraceHandle,
-              'name': 'test',
-              'metrics': <String, int>{},
-              'attributes': <String, String>{},
-            },
-          ),
-        ]);
-      });
-
-      test('incrementCounter', () async {
-        final Trace trace = performance.newTrace('test');
-
-        // ignore: deprecated_member_use_from_same_package
-        trace.incrementCounter('counter1');
-
-        // ignore: deprecated_member_use_from_same_package
-        trace.incrementCounter('counter2');
-        // ignore: deprecated_member_use_from_same_package
-        trace.incrementCounter('counter2');
-
-        // ignore: deprecated_member_use_from_same_package
-        trace.incrementCounter('counter3', 5);
-        // ignore: deprecated_member_use_from_same_package
-        trace.incrementCounter('counter3', 5);
-
-        // ignore: deprecated_member_use_from_same_package
-        trace.incrementCounter('counter4', -5);
-
-        await trace.start();
-        await trace.stop();
-
-        expect(log, <Matcher>[
-          isMethodCall(
-            'Trace#start',
-            arguments: <String, Object>{
-              'handle': currentTraceHandle,
-              'name': 'test',
-            },
-          ),
-          isMethodCall(
-            'Trace#stop',
-            arguments: <String, dynamic>{
-              'handle': currentTraceHandle,
-              'name': 'test',
-              'metrics': <String, int>{
-                'counter1': 1,
-                'counter2': 2,
-                'counter3': 10,
-                'counter4': -5,
-              },
-              'attributes': <String, String>{},
-            },
-          ),
+        expect(traceLog, <Matcher>[
+          isMethodCall('Trace#stop', arguments: null),
         ]);
       });
 
       test('incrementMetric', () async {
-        final Trace trace = performance.newTrace('test');
-        trace.incrementMetric('metric1', 1);
-
-        trace.incrementMetric('metric2', 1);
-        trace.incrementMetric('metric2', 1);
-
-        trace.incrementMetric('metric3', 5);
-        trace.incrementMetric('metric3', 5);
+        await pumpEventQueue();
 
-        trace.incrementMetric('metric4', -5);
+        final String name = 'counter1';
+        final int value = 45;
 
-        await trace.start();
-        await trace.stop();
+        testTrace.incrementMetric(name, value);
 
-        expect(log, <Matcher>[
+        expect(traceLog, <Matcher>[
           isMethodCall(
-            'Trace#start',
-            arguments: <String, Object>{
-              'handle': currentTraceHandle,
-              'name': 'test',
-            },
-          ),
-          isMethodCall(
-            'Trace#stop',
+            'Trace#incrementMetric',
             arguments: <String, dynamic>{
-              'handle': currentTraceHandle,
-              'name': 'test',
-              'metrics': <String, int>{
-                'metric1': 1,
-                'metric2': 2,
-                'metric3': 10,
-                'metric4': -5,
-              },
-              'attributes': <String, String>{},
+              'name': name,
+              'value': value,
             },
           ),
         ]);
@@ -267,106 +179,115 @@ void main() {
 
     group('$HttpMetric', () {
       HttpMetric testMetric;
+      final List<MethodCall> httpMetricLog = <MethodCall>[];
 
       setUp(() {
         testMetric = performance.newHttpMetric(
           'https://google.com',
           HttpMethod.Get,
         );
+        testMetric.channel
+            .setMockMethodCallHandler((MethodCall methodCall) async {
+          httpMetricLog.add(methodCall);
+          switch (methodCall.method) {
+            case 'FirebasePerformance#isPerformanceCollectionEnabled':
+              return true;
+            default:
+              return null;
+          }
+        });
+        httpMetricLog.clear();
       });
 
       test('start', () async {
+        await pumpEventQueue();
+
         await testMetric.start();
 
-        expect(log, <Matcher>[
-          isMethodCall(
-            'HttpMetric#start',
-            arguments: <String, Object>{
-              'handle': currentHttpMetricHandle,
-              'url': 'https://google.com',
-              'httpMethod': HttpMethod.Get.index,
-            },
-          ),
+        expect(httpMetricLog, <Matcher>[
+          isMethodCall('HttpMetric#start', arguments: null),
         ]);
       });
 
       test('stop', () async {
-        testMetric.httpResponseCode = 1;
-        testMetric.requestPayloadSize = 5000000;
-        testMetric.responseContentType = 'text/html';
-        testMetric.responsePayloadSize = 1992304820934820;
+        await pumpEventQueue();
 
-        await testMetric.start();
         await testMetric.stop();
 
-        expect(log, <Matcher>[
-          isMethodCall(
-            'HttpMetric#start',
-            arguments: <String, Object>{
-              'handle': currentHttpMetricHandle,
-              'url': 'https://google.com',
-              'httpMethod': HttpMethod.Get.index,
-            },
-          ),
-          isMethodCall(
-            'HttpMetric#stop',
-            arguments: <String, dynamic>{
-              'handle': currentHttpMetricHandle,
-              'httpResponseCode': 1,
-              'requestPayloadSize': 5000000,
-              'responseContentType': 'text/html',
-              'responsePayloadSize': 1992304820934820,
-              'attributes': <String, String>{},
-            },
-          ),
+        expect(httpMetricLog, <Matcher>[
+          isMethodCall('HttpMetric#stop', arguments: null),
         ]);
       });
     });
 
     group('$PerformanceAttributes', () {
-      PerformanceAttributes attributes;
+      final PerformanceAttributes attributes = MockPerformanceAttributes();
+      final List<MethodCall> attributeLog = <MethodCall>[];
+      final Map<dynamic, dynamic> getAttributesResult = <dynamic, dynamic>{
+        'a1': 'hello',
+        'a2': 'friend',
+      };
 
       setUp(() {
-        attributes = MockPerformanceAttributes();
+        MockPerformanceAttributes._channel
+            .setMockMethodCallHandler((MethodCall methodCall) async {
+          attributeLog.add(methodCall);
+          if (methodCall.method == 'PerformanceAttributes#getAttributes') {
+            return getAttributesResult;
+          }
+
+          return null;
+        });
+        attributeLog.clear();
       });
 
       test('putAttribute', () async {
-        attributes.putAttribute('attr1', 'apple');
-        attributes.putAttribute('attr2', 'are');
-        expect(attributes.attributes, <String, String>{
-          'attr1': 'apple',
-          'attr2': 'are',
-        });
+        final String attribute = 'attr1';
+        final String value = 'apple';
+        await attributes.putAttribute(attribute, value);
 
-        attributes.putAttribute('attr1', 'delicious');
-        expect(attributes.attributes, <String, String>{
-          'attr1': 'delicious',
-          'attr2': 'are',
-        });
+        expect(attributeLog, <Matcher>[
+          isMethodCall(
+            'PerformanceAttributes#putAttribute',
+            arguments: <String, dynamic>{
+              'attribute': attribute,
+              'value': value,
+            },
+          ),
+        ]);
       });
 
       test('removeAttribute', () async {
-        attributes.putAttribute('attr1', 'apple');
-        attributes.putAttribute('attr2', 'are');
-        attributes.removeAttribute('no-attr');
-        expect(attributes.attributes, <String, String>{
-          'attr1': 'apple',
-          'attr2': 'are',
-        });
+        final String attribute = 'attr1';
+        await attributes.removeAttribute(attribute);
 
-        attributes.removeAttribute('attr1');
-        expect(attributes.attributes, <String, String>{
-          'attr2': 'are',
-        });
+        expect(attributeLog, <Matcher>[
+          isMethodCall(
+            'PerformanceAttributes#removeAttribute',
+            arguments: attribute,
+          ),
+        ]);
       });
 
-      test('getAttribute', () {
-        attributes.putAttribute('attr1', 'apple');
-        attributes.putAttribute('attr2', 'are');
-        expect(attributes.getAttribute('attr1'), 'apple');
+      test('getAttributes', () async {
+        final Map<String, String> result = await attributes.getAttributes();
+
+        expect(attributeLog, <Matcher>[
+          isMethodCall(
+            'PerformanceAttributes#getAttributes',
+            arguments: null,
+          ),
+        ]);
 
-        expect(attributes.getAttribute('attr3'), isNull);
+        expect(result, getAttributesResult);
       });
     });
   });
 }
+
+class MockPerformanceAttributes extends PerformanceAttributes {
+  static MethodChannel _channel = const MethodChannel('testMethodChannel');
+
+  @override
+  MethodChannel get methodChannel => _channel;
+}

From 08d976f2dbef722552286ad3548eb02d28dbf92b Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 14:39:24 -0700
Subject: [PATCH 10/40] Extra space

---
 .../flutter/plugins/firebaseperformance/FlutterHttpMetric.java   | 1 -
 1 file changed, 1 deletion(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index d3073f37b52f..927a94719fea 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -127,7 +127,6 @@ private void setResponsePayloadSize(MethodCall call, MethodChannel.Result result
     result.success(null);
   }
 
-
   private void putAttribute(MethodCall call, MethodChannel.Result result) {
     final String attribute = call.argument("attribute");
     final String value = call.argument("value");

From 8a8ab7725817205f3389551a789d5d7053e6ad6a Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 15:01:59 -0700
Subject: [PATCH 11/40] Remove awaits and ayncs

---
 .../test/firebase_performance_test.dart       | 101 ++++++++----------
 1 file changed, 46 insertions(+), 55 deletions(-)

diff --git a/packages/firebase_performance/test/firebase_performance_test.dart b/packages/firebase_performance/test/firebase_performance_test.dart
index cf45623f5f41..42b8f67e7c24 100644
--- a/packages/firebase_performance/test/firebase_performance_test.dart
+++ b/packages/firebase_performance/test/firebase_performance_test.dart
@@ -11,6 +11,7 @@ void main() {
   group('$FirebasePerformance', () {
     final FirebasePerformance performance = FirebasePerformance.instance;
     final List<MethodCall> log = <MethodCall>[];
+    bool isPerformanceCollectionEnabledResult;
 
     setUp(() {
       FirebasePerformance.channel
@@ -18,7 +19,7 @@ void main() {
         log.add(methodCall);
         switch (methodCall.method) {
           case 'FirebasePerformance#isPerformanceCollectionEnabled':
-            return true;
+            return isPerformanceCollectionEnabledResult;
           default:
             return null;
         }
@@ -27,20 +28,29 @@ void main() {
     });
 
     test('isPerformanceCollectionEnabled', () async {
+      isPerformanceCollectionEnabledResult = true;
       final bool enabled = await performance.isPerformanceCollectionEnabled();
-
       expect(enabled, isTrue);
+
+      isPerformanceCollectionEnabledResult = false;
+      final bool disabled = await performance.isPerformanceCollectionEnabled();
+      expect(disabled, isFalse);
+
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#isPerformanceCollectionEnabled',
           arguments: null,
         ),
+        isMethodCall(
+          'FirebasePerformance#isPerformanceCollectionEnabled',
+          arguments: null,
+        ),
       ]);
     });
 
-    test('setPerformanceCollectionEnabled', () async {
-      await performance.setPerformanceCollectionEnabled(true);
-      await performance.setPerformanceCollectionEnabled(false);
+    test('setPerformanceCollectionEnabled', () {
+      performance.setPerformanceCollectionEnabled(true);
+      performance.setPerformanceCollectionEnabled(false);
 
       expect(log, <Matcher>[
         isMethodCall(
@@ -54,11 +64,9 @@ void main() {
       ]);
     });
 
-    test('newTrace', () async {
+    test('newTrace', () {
       final Trace trace = performance.newTrace('test-trace');
 
-      await pumpEventQueue();
-
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#newTrace',
@@ -70,7 +78,7 @@ void main() {
       ]);
     });
 
-    test('newHttpMetric', () async {
+    test('newHttpMetric', () {
       final String url = 'https://google.com';
 
       final HttpMetric metric = performance.newHttpMetric(
@@ -78,8 +86,6 @@ void main() {
         HttpMethod.Connect,
       );
 
-      await pumpEventQueue();
-
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#newHttpMetric',
@@ -92,30 +98,25 @@ void main() {
       ]);
     });
 
-    test('$HttpMethod', () async {
+    test('$HttpMethod', () {
       final String url = 'https://google.com';
+      final HttpMethod method = HttpMethod.Connect;
 
-      for (HttpMethod method in HttpMethod.values) {
-        final HttpMetric metric = performance.newHttpMetric(
-          'https://google.com',
-          method,
-        );
-
-        await pumpEventQueue();
-
-        expect(log, <Matcher>[
-          isMethodCall(
-            'FirebasePerformance#newHttpMetric',
-            arguments: <String, dynamic>{
-              'channelName': metric.channel.name,
-              'url': url,
-              'httpMethod': method.toString(),
-            },
-          ),
-        ]);
+      final HttpMetric metric = performance.newHttpMetric(
+        'https://google.com',
+        method,
+      );
 
-        log.clear();
-      }
+      expect(log, <Matcher>[
+        isMethodCall(
+          'FirebasePerformance#newHttpMetric',
+          arguments: <String, dynamic>{
+            'channelName': metric.channel.name,
+            'url': url,
+            'httpMethod': method.toString(),
+          },
+        ),
+      ]);
     });
 
     group('$Trace', () {
@@ -137,29 +138,23 @@ void main() {
         traceLog.clear();
       });
 
-      test('start', () async {
-        await pumpEventQueue();
-
-        await testTrace.start();
+      test('start', () {
+        testTrace.start();
 
         expect(traceLog, <Matcher>[
           isMethodCall('Trace#start', arguments: null),
         ]);
       });
 
-      test('stop', () async {
-        await pumpEventQueue();
-
-        await testTrace.stop();
+      test('stop', () {
+        testTrace.stop();
 
         expect(traceLog, <Matcher>[
           isMethodCall('Trace#stop', arguments: null),
         ]);
       });
 
-      test('incrementMetric', () async {
-        await pumpEventQueue();
-
+      test('incrementMetric', () {
         final String name = 'counter1';
         final int value = 45;
 
@@ -199,20 +194,16 @@ void main() {
         httpMetricLog.clear();
       });
 
-      test('start', () async {
-        await pumpEventQueue();
-
-        await testMetric.start();
+      test('start', () {
+        testMetric.start();
 
         expect(httpMetricLog, <Matcher>[
           isMethodCall('HttpMetric#start', arguments: null),
         ]);
       });
 
-      test('stop', () async {
-        await pumpEventQueue();
-
-        await testMetric.stop();
+      test('stop', () {
+        testMetric.stop();
 
         expect(httpMetricLog, <Matcher>[
           isMethodCall('HttpMetric#stop', arguments: null),
@@ -241,10 +232,10 @@ void main() {
         attributeLog.clear();
       });
 
-      test('putAttribute', () async {
+      test('putAttribute', () {
         final String attribute = 'attr1';
         final String value = 'apple';
-        await attributes.putAttribute(attribute, value);
+        attributes.putAttribute(attribute, value);
 
         expect(attributeLog, <Matcher>[
           isMethodCall(
@@ -257,9 +248,9 @@ void main() {
         ]);
       });
 
-      test('removeAttribute', () async {
+      test('removeAttribute', () {
         final String attribute = 'attr1';
-        await attributes.removeAttribute(attribute);
+        attributes.removeAttribute(attribute);
 
         expect(attributeLog, <Matcher>[
           isMethodCall(

From 3c3ed91e6cc27c89e8c37e151529c85ce1d9aea9 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 15:02:44 -0700
Subject: [PATCH 12/40] Remove mentions of asynchronous

---
 .../lib/src/firebase_performance.dart                     | 2 +-
 packages/firebase_performance/lib/src/http_metric.dart    | 2 +-
 packages/firebase_performance/lib/src/trace.dart          | 8 ++++----
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index f1640665ca64..5b9e044b47e1 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -33,7 +33,7 @@ class FirebasePerformance {
     );
   }
 
-  /// Enables or disables performance monitoring asynchronously.
+  /// Enables or disables performance monitoring.
   ///
   /// This setting is persisted and applied on future invocations of your
   /// application. By default, performance monitoring is enabled.
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index aeabb8024c95..67b3ba1b40ab 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -56,7 +56,7 @@ class HttpMetric extends PerformanceAttributes {
     );
   }
 
-  /// Starts this [HttpMetric] asynchronously.
+  /// Starts this [HttpMetric].
   ///
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index cda5c066fecc..936f9204d55c 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -30,7 +30,7 @@ class Trace extends PerformanceAttributes {
   @override
   MethodChannel get methodChannel => channel;
 
-  /// Starts this [Trace] asynchronously.
+  /// Starts this [Trace].
   ///
   /// Can only be called once.
   ///
@@ -40,7 +40,7 @@ class Trace extends PerformanceAttributes {
     return channel.invokeMethod<void>('$Trace#start');
   }
 
-  /// Stops this [Trace] asynchronously.
+  /// Stops this [Trace].
   ///
   /// Can only be called once and only after start() Data collected is
   /// automatically sent to the associated Firebase console after stop() is
@@ -52,7 +52,7 @@ class Trace extends PerformanceAttributes {
     return channel.invokeMethod<void>('$Trace#stop');
   }
 
-  /// Increments the metric with the given name asynchronously.
+  /// Increments the metric with the given name.
   ///
   /// If the metric does not exist, a new one will be created. If the trace has
   /// not been started or has already been stopped, returns immediately without
@@ -64,7 +64,7 @@ class Trace extends PerformanceAttributes {
     );
   }
 
-  /// Sets the value of the metric with the given name asynchronously.
+  /// Sets the value of the metric with the given name.
   ///
   /// If a metric with the given name doesn't exist, a new one will be created.
   /// If the trace has not been started or has already been stopped, returns

From bd971abcb02f25cc535d9017747a1eb4a272b2f7 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 23 Apr 2019 16:56:29 -0700
Subject: [PATCH 13/40] cache state

---
 .../lib/src/firebase_performance.dart         |  2 +-
 .../lib/src/http_metric.dart                  | 20 +++++++++++
 .../lib/src/performance_attributes.dart       | 24 +++++++++++++-
 .../firebase_performance/lib/src/trace.dart   | 26 +++++++++++++++
 .../test/firebase_performance_test.dart       | 33 +++++++++----------
 5 files changed, 86 insertions(+), 19 deletions(-)

diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index 5b9e044b47e1..d4843dcf245a 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -37,7 +37,7 @@ class FirebasePerformance {
   ///
   /// This setting is persisted and applied on future invocations of your
   /// application. By default, performance monitoring is enabled.
-  Future<void> setPerformanceCollectionEnabled(bool enable) async {
+  Future<void> setPerformanceCollectionEnabled(bool enable) {
     return channel.invokeMethod<void>(
       'FirebasePerformance#setPerformanceCollectionEnabled',
       enable,
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index 67b3ba1b40ab..c7669571b5c1 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -21,11 +21,19 @@ class HttpMetric extends PerformanceAttributes {
   @visibleForTesting
   final MethodChannel channel;
 
+  @override
+  bool _hasStarted = false;
+
+  @override
+  bool _hasStopped = false;
+
   @override
   MethodChannel get methodChannel => channel;
 
   /// HttpResponse code of the request.
   set httpResponseCode(int httpResponseCode) {
+    if (_hasStopped) return;
+
     channel.invokeMethod<void>(
       '$HttpMetric#httpResponseCode',
       httpResponseCode,
@@ -34,6 +42,8 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Size of the request payload.
   set requestPayloadSize(int requestPayloadSize) {
+    if (_hasStopped) return;
+
     channel.invokeMethod<void>(
       '$HttpMetric#requestPayloadSize',
       requestPayloadSize,
@@ -42,6 +52,8 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Content type of the response such as text/html, application/json, etc...
   set responseContentType(String responseContentType) {
+    if (_hasStopped) return;
+
     channel.invokeMethod<void>(
       '$HttpMetric#responseContentType',
       responseContentType,
@@ -50,6 +62,8 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Size of the response payload.
   set responsePayloadSize(int responsePayloadSize) {
+    if (_hasStopped) return;
+
     channel.invokeMethod<void>(
       '$HttpMetric#responsePayloadSize',
       responsePayloadSize,
@@ -61,6 +75,9 @@ class HttpMetric extends PerformanceAttributes {
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
+    if (_hasStarted || _hasStopped) return Future<void>.value(null);
+
+    _hasStarted = true;
     return channel.invokeMethod<void>('$HttpMetric#start');
   }
 
@@ -73,6 +90,9 @@ class HttpMetric extends PerformanceAttributes {
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
+    if (_hasStopped) return Future<void>.value(null);
+
+    _hasStopped = true;
     return channel.invokeMethod<void>('$HttpMetric#stop');
   }
 }
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index b74869e11878..09411e2d9079 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -15,8 +15,12 @@ abstract class PerformanceAttributes {
   /// Maximum allowed number of attributes that can be added.
   static const int maxCustomAttributes = 5;
 
+  final Map<String, String> _attributes = <String, String>{};
+
   @visibleForTesting
   MethodChannel get methodChannel;
+  bool get _hasStarted;
+  bool get _hasStopped;
 
   /// Sets a String [value] for the specified [attribute].
   ///
@@ -28,6 +32,15 @@ abstract class PerformanceAttributes {
   /// characters. Value of the attribute has max length of
   /// [maxAttributeValueLength] characters.
   Future<void> putAttribute(String attribute, String value) {
+    if (!_hasStarted ||
+        _hasStopped ||
+        attribute.length > maxAttributeKeyLength ||
+        value.length > maxAttributeValueLength ||
+        _attributes.length == 5) {
+      return Future<void>.value(null);
+    }
+
+    _attributes[attribute] = value;
     return methodChannel.invokeMethod<void>(
       '$PerformanceAttributes#putAttribute',
       <String, String>{'attribute': attribute, 'value': value},
@@ -36,14 +49,23 @@ abstract class PerformanceAttributes {
 
   /// Removes an already added [attribute].
   Future<void> removeAttribute(String attribute) {
+    if (!_hasStarted || _hasStopped) return Future<void>.value(null);
+
+    _attributes.remove(attribute);
     return methodChannel.invokeMethod<void>(
       '$PerformanceAttributes#removeAttribute',
       attribute,
     );
   }
 
-  /// All [attribute]s added.
+  /// All attributes added.
   Future<Map<String, String>> getAttributes() {
+    if (_hasStopped) {
+      return Future<Map<String, String>>.value(Map<String, String>.unmodifiable(
+        _attributes,
+      ));
+    }
+
     return methodChannel.invokeMapMethod<String, String>(
       '$PerformanceAttributes#getAttributes',
     );
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 936f9204d55c..fc406199f900 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -27,6 +27,14 @@ class Trace extends PerformanceAttributes {
   @visibleForTesting
   final MethodChannel channel;
 
+  final Map<String, int> _metrics = <String, int>{};
+
+  @override
+  bool _hasStarted = false;
+
+  @override
+  bool _hasStopped = false;
+
   @override
   MethodChannel get methodChannel => channel;
 
@@ -37,6 +45,9 @@ class Trace extends PerformanceAttributes {
   /// Using ```await``` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
+    if (_hasStarted || _hasStopped) return Future<void>.value(null);
+
+    _hasStarted = true;
     return channel.invokeMethod<void>('$Trace#start');
   }
 
@@ -49,6 +60,9 @@ class Trace extends PerformanceAttributes {
   ///
   /// Not necessary to use ```await``` with this method.
   Future<void> stop() {
+    if (_hasStopped) return Future<void>.value(null);
+
+    _hasStopped = true;
     return channel.invokeMethod<void>('$Trace#stop');
   }
 
@@ -58,6 +72,11 @@ class Trace extends PerformanceAttributes {
   /// not been started or has already been stopped, returns immediately without
   /// taking action.
   Future<void> incrementMetric(String name, int value) {
+    if (!_hasStarted || _hasStopped || _metrics[name] == null) {
+      return Future<void>.value(null);
+    }
+
+    _metrics[name] += value;
     return channel.invokeMethod<void>(
       '$Trace#incrementMetric',
       <String, dynamic>{'name': name, 'value': value},
@@ -70,6 +89,9 @@ class Trace extends PerformanceAttributes {
   /// If the trace has not been started or has already been stopped, returns
   /// immediately without taking action.
   Future<void> putMetric(String name, int value) {
+    if (!_hasStarted || _hasStopped) return Future<void>.value(null);
+
+    _metrics[name] = value;
     return channel.invokeMethod<void>(
       '$Trace#putMetric',
       <String, dynamic>{'name': name, 'value': value},
@@ -81,6 +103,10 @@ class Trace extends PerformanceAttributes {
   /// If a metric with the given name doesn't exist, it is NOT created and a 0
   /// is returned.
   Future<int> getMetric(String name) {
+    if (_hasStopped) {
+      return Future<int>.value(_metrics[name] ?? 0);
+    }
+
     return channel.invokeMethod<int>(
       '$Trace#getMetric',
       <String, dynamic>{'name': name},
diff --git a/packages/firebase_performance/test/firebase_performance_test.dart b/packages/firebase_performance/test/firebase_performance_test.dart
index 42b8f67e7c24..2dd5fe122998 100644
--- a/packages/firebase_performance/test/firebase_performance_test.dart
+++ b/packages/firebase_performance/test/firebase_performance_test.dart
@@ -157,16 +157,18 @@ void main() {
       test('incrementMetric', () {
         final String name = 'counter1';
         final int value = 45;
+        final int increment = 3;
 
-        testTrace.incrementMetric(name, value);
+        testTrace.start();
+        testTrace.putMetric(name, value);
+        traceLog.clear();
+
+        testTrace.incrementMetric(name, increment);
 
         expect(traceLog, <Matcher>[
           isMethodCall(
             'Trace#incrementMetric',
-            arguments: <String, dynamic>{
-              'name': name,
-              'value': value,
-            },
+            arguments: <String, dynamic>{'name': name, 'value': increment},
           ),
         ]);
       });
@@ -212,7 +214,7 @@ void main() {
     });
 
     group('$PerformanceAttributes', () {
-      final PerformanceAttributes attributes = MockPerformanceAttributes();
+      Trace attributeTrace;
       final List<MethodCall> attributeLog = <MethodCall>[];
       final Map<dynamic, dynamic> getAttributesResult = <dynamic, dynamic>{
         'a1': 'hello',
@@ -220,7 +222,8 @@ void main() {
       };
 
       setUp(() {
-        MockPerformanceAttributes._channel
+        attributeTrace = performance.newTrace('trace');
+        attributeTrace.channel
             .setMockMethodCallHandler((MethodCall methodCall) async {
           attributeLog.add(methodCall);
           if (methodCall.method == 'PerformanceAttributes#getAttributes') {
@@ -229,13 +232,16 @@ void main() {
 
           return null;
         });
+
+        attributeTrace.start();
         attributeLog.clear();
       });
 
       test('putAttribute', () {
         final String attribute = 'attr1';
         final String value = 'apple';
-        attributes.putAttribute(attribute, value);
+
+        attributeTrace.putAttribute(attribute, value);
 
         expect(attributeLog, <Matcher>[
           isMethodCall(
@@ -250,7 +256,7 @@ void main() {
 
       test('removeAttribute', () {
         final String attribute = 'attr1';
-        attributes.removeAttribute(attribute);
+        attributeTrace.removeAttribute(attribute);
 
         expect(attributeLog, <Matcher>[
           isMethodCall(
@@ -261,7 +267,7 @@ void main() {
       });
 
       test('getAttributes', () async {
-        final Map<String, String> result = await attributes.getAttributes();
+        final Map<String, String> result = await attributeTrace.getAttributes();
 
         expect(attributeLog, <Matcher>[
           isMethodCall(
@@ -275,10 +281,3 @@ void main() {
     });
   });
 }
-
-class MockPerformanceAttributes extends PerformanceAttributes {
-  static MethodChannel _channel = const MethodChannel('testMethodChannel');
-
-  @override
-  MethodChannel get methodChannel => _channel;
-}

From 849d62566aa2cb3246acff8a7d14ca008a24b8c2 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 24 Apr 2019 11:46:02 -0700
Subject: [PATCH 14/40] Comments/Testings/Variables/Misc

---
 .../test_driver/firebase_performance.dart     |  3 ++
 .../lib/src/firebase_performance.dart         | 11 +++++
 .../lib/src/http_metric.dart                  | 47 ++++++++++++++++---
 .../lib/src/performance_attributes.dart       | 11 +++--
 .../firebase_performance/lib/src/trace.dart   | 26 +++++-----
 5 files changed, 71 insertions(+), 27 deletions(-)

diff --git a/packages/firebase_performance/example/test_driver/firebase_performance.dart b/packages/firebase_performance/example/test_driver/firebase_performance.dart
index fcabfe11f239..295a5da94ad2 100644
--- a/packages/firebase_performance/example/test_driver/firebase_performance.dart
+++ b/packages/firebase_performance/example/test_driver/firebase_performance.dart
@@ -25,6 +25,8 @@ void main() {
       expect(disabled, isFalse);
     });
 
+    // TODO(bparrishMines): Rewrite integration test when iOS portion is written.
+    /*
     test('metric', () async {
       final Trace trace = performance.newTrace('test');
       trace.putAttribute('testAttribute', 'foo');
@@ -37,5 +39,6 @@ void main() {
       expect(trace.getAttribute('testAttribute2'), null);
       expect(trace.getAttribute('testMetric'), null);
     });
+    */
   });
 }
diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index d4843dcf245a..9a74c3d3632d 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -79,4 +79,15 @@ class FirebasePerformance {
     final MethodChannel channel = MethodChannel(channelName);
     return HttpMetric._(channel);
   }
+
+  /// Creates a [Trace] object with given [name] and starts the trace.
+  ///
+  /// The [name] requires no leading or trailing whitespace, no leading
+  /// underscore _ character, max length of [Trace.maxTraceNameLength]
+  /// characters.
+  static Future<Trace> startTrace(String name) async {
+    final Trace trace = instance.newTrace(name);
+    await trace.start();
+    return trace;
+  }
 }
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index c7669571b5c1..12ec1dd895f8 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -18,22 +18,41 @@ part of firebase_performance;
 class HttpMetric extends PerformanceAttributes {
   HttpMetric._(this.channel);
 
-  @visibleForTesting
-  final MethodChannel channel;
-
   @override
   bool _hasStarted = false;
 
   @override
   bool _hasStopped = false;
 
+  int _httpResponseCode;
+  int _requestPayloadSize;
+  String _responseContentType;
+  int _responsePayloadSize;
+
+  @visibleForTesting
   @override
-  MethodChannel get methodChannel => channel;
+  final MethodChannel channel;
+
+  /// HttpResponse code of the request.
+  int get httpResponseCode => _httpResponseCode;
+
+  /// Size of the request payload.
+  int get requestPayloadSize => _requestPayloadSize;
+
+  /// Content type of the response such as text/html, application/json, etc...
+  String get responseContentType => _responseContentType;
+
+  /// Size of the response payload.
+  int get responsePayloadSize => _responsePayloadSize;
 
   /// HttpResponse code of the request.
+  ///
+  /// If the [HttpMetric] has already been stopped, returns immediately without
+  /// taking action.
   set httpResponseCode(int httpResponseCode) {
     if (_hasStopped) return;
 
+    _httpResponseCode = httpResponseCode;
     channel.invokeMethod<void>(
       '$HttpMetric#httpResponseCode',
       httpResponseCode,
@@ -41,9 +60,13 @@ class HttpMetric extends PerformanceAttributes {
   }
 
   /// Size of the request payload.
+  ///
+  /// If the [HttpMetric] has already been stopped, returns immediately without
+  /// taking action.
   set requestPayloadSize(int requestPayloadSize) {
     if (_hasStopped) return;
 
+    _requestPayloadSize = requestPayloadSize;
     channel.invokeMethod<void>(
       '$HttpMetric#requestPayloadSize',
       requestPayloadSize,
@@ -51,9 +74,13 @@ class HttpMetric extends PerformanceAttributes {
   }
 
   /// Content type of the response such as text/html, application/json, etc...
+  ///
+  /// If the [HttpMetric] has already been stopped, returns immediately without
+  /// taking action.
   set responseContentType(String responseContentType) {
     if (_hasStopped) return;
 
+    _responseContentType = responseContentType;
     channel.invokeMethod<void>(
       '$HttpMetric#responseContentType',
       responseContentType,
@@ -61,9 +88,13 @@ class HttpMetric extends PerformanceAttributes {
   }
 
   /// Size of the response payload.
+  ///
+  /// If the [HttpMetric] has already been stopped, returns immediately without
+  /// taking action.
   set responsePayloadSize(int responsePayloadSize) {
     if (_hasStopped) return;
 
+    _responsePayloadSize = responsePayloadSize;
     channel.invokeMethod<void>(
       '$HttpMetric#responsePayloadSize',
       responsePayloadSize,
@@ -72,10 +103,12 @@ class HttpMetric extends PerformanceAttributes {
 
   /// Starts this [HttpMetric].
   ///
-  /// Using ```await``` with this method is only necessary when accurate timing
+  /// Can only be called once.
+  ///
+  /// Using `await` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    if (_hasStarted || _hasStopped) return Future<void>.value(null);
+    if (_hasStopped) return Future<void>.value(null);
 
     _hasStarted = true;
     return channel.invokeMethod<void>('$HttpMetric#start');
@@ -88,7 +121,7 @@ class HttpMetric extends PerformanceAttributes {
   /// called. You can confirm that Performance Monitoring results appear in the
   /// Firebase console. Results should appear within 12 hours.
   ///
-  /// Not necessary to use ```await``` with this method.
+  /// Not necessary to use `await` with this method.
   Future<void> stop() {
     if (_hasStopped) return Future<void>.value(null);
 
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index 09411e2d9079..de2f6452c41d 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -17,11 +17,12 @@ abstract class PerformanceAttributes {
 
   final Map<String, String> _attributes = <String, String>{};
 
-  @visibleForTesting
-  MethodChannel get methodChannel;
   bool get _hasStarted;
   bool get _hasStopped;
 
+  @visibleForTesting
+  MethodChannel get channel;
+
   /// Sets a String [value] for the specified [attribute].
   ///
   /// Updates the value of the attribute if the attribute already exists.
@@ -41,7 +42,7 @@ abstract class PerformanceAttributes {
     }
 
     _attributes[attribute] = value;
-    return methodChannel.invokeMethod<void>(
+    return channel.invokeMethod<void>(
       '$PerformanceAttributes#putAttribute',
       <String, String>{'attribute': attribute, 'value': value},
     );
@@ -52,7 +53,7 @@ abstract class PerformanceAttributes {
     if (!_hasStarted || _hasStopped) return Future<void>.value(null);
 
     _attributes.remove(attribute);
-    return methodChannel.invokeMethod<void>(
+    return channel.invokeMethod<void>(
       '$PerformanceAttributes#removeAttribute',
       attribute,
     );
@@ -66,7 +67,7 @@ abstract class PerformanceAttributes {
       ));
     }
 
-    return methodChannel.invokeMapMethod<String, String>(
+    return channel.invokeMapMethod<String, String>(
       '$PerformanceAttributes#getAttributes',
     );
   }
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index fc406199f900..484e2e3fba37 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -24,9 +24,6 @@ class Trace extends PerformanceAttributes {
   /// Maximum allowed length of the name of a [Trace].
   static const int maxTraceNameLength = 100;
 
-  @visibleForTesting
-  final MethodChannel channel;
-
   final Map<String, int> _metrics = <String, int>{};
 
   @override
@@ -35,17 +32,18 @@ class Trace extends PerformanceAttributes {
   @override
   bool _hasStopped = false;
 
+  @visibleForTesting
   @override
-  MethodChannel get methodChannel => channel;
+  final MethodChannel channel;
 
   /// Starts this [Trace].
   ///
   /// Can only be called once.
   ///
-  /// Using ```await``` with this method is only necessary when accurate timing
+  /// Using `await` with this method is only necessary when accurate timing
   /// is relevant.
   Future<void> start() {
-    if (_hasStarted || _hasStopped) return Future<void>.value(null);
+    if (_hasStopped) return Future<void>.value(null);
 
     _hasStarted = true;
     return channel.invokeMethod<void>('$Trace#start');
@@ -58,7 +56,7 @@ class Trace extends PerformanceAttributes {
   /// called. You can confirm that Performance Monitoring results appear in the
   /// Firebase console. Results should appear within 12 hours.
   ///
-  /// Not necessary to use ```await``` with this method.
+  /// Not necessary to use `await` with this method.
   Future<void> stop() {
     if (_hasStopped) return Future<void>.value(null);
 
@@ -66,9 +64,9 @@ class Trace extends PerformanceAttributes {
     return channel.invokeMethod<void>('$Trace#stop');
   }
 
-  /// Increments the metric with the given name.
+  /// Increments the metric with the given [name].
   ///
-  /// If the metric does not exist, a new one will be created. If the trace has
+  /// If the metric does not exist, a new one will be created. If the [Trace] has
   /// not been started or has already been stopped, returns immediately without
   /// taking action.
   Future<void> incrementMetric(String name, int value) {
@@ -83,10 +81,10 @@ class Trace extends PerformanceAttributes {
     );
   }
 
-  /// Sets the value of the metric with the given name.
+  /// Sets the [value] of the metric with the given [name].
   ///
   /// If a metric with the given name doesn't exist, a new one will be created.
-  /// If the trace has not been started or has already been stopped, returns
+  /// If the [Trace] has not been started or has already been stopped, returns
   /// immediately without taking action.
   Future<void> putMetric(String name, int value) {
     if (!_hasStarted || _hasStopped) return Future<void>.value(null);
@@ -98,14 +96,12 @@ class Trace extends PerformanceAttributes {
     );
   }
 
-  /// Gets the value of the metric with the given name.
+  /// Gets the value of the metric with the given [name].
   ///
   /// If a metric with the given name doesn't exist, it is NOT created and a 0
   /// is returned.
   Future<int> getMetric(String name) {
-    if (_hasStopped) {
-      return Future<int>.value(_metrics[name] ?? 0);
-    }
+    if (_hasStopped) return Future<int>.value(_metrics[name] ?? 0);
 
     return channel.invokeMethod<int>(
       '$Trace#getMetric',

From b08ad05bb12f46165f4b0f569f518fb2acca4a06 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 24 Apr 2019 12:08:26 -0700
Subject: [PATCH 15/40] Change putMetric to setMetric to match iOS API. Also
 add name variable

---
 .../lib/src/firebase_performance.dart                    | 2 +-
 packages/firebase_performance/lib/src/trace.dart         | 9 ++++++---
 .../test/firebase_performance_test.dart                  | 2 +-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index 9a74c3d3632d..571e6b8063bd 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -59,7 +59,7 @@ class FirebasePerformance {
     );
 
     final MethodChannel channel = MethodChannel(channelName);
-    return Trace._(channel);
+    return Trace._(channel, name);
   }
 
   /// Creates [HttpMetric] for collecting performance for one request/response.
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 484e2e3fba37..20e240385eb7 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -19,7 +19,7 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class Trace extends PerformanceAttributes {
-  Trace._(this.channel);
+  Trace._(this.channel, this.name);
 
   /// Maximum allowed length of the name of a [Trace].
   static const int maxTraceNameLength = 100;
@@ -36,6 +36,9 @@ class Trace extends PerformanceAttributes {
   @override
   final MethodChannel channel;
 
+  /// Name representing this [Trace] on the Firebase Console.
+  final String name;
+
   /// Starts this [Trace].
   ///
   /// Can only be called once.
@@ -86,12 +89,12 @@ class Trace extends PerformanceAttributes {
   /// If a metric with the given name doesn't exist, a new one will be created.
   /// If the [Trace] has not been started or has already been stopped, returns
   /// immediately without taking action.
-  Future<void> putMetric(String name, int value) {
+  Future<void> setMetric(String name, int value) {
     if (!_hasStarted || _hasStopped) return Future<void>.value(null);
 
     _metrics[name] = value;
     return channel.invokeMethod<void>(
-      '$Trace#putMetric',
+      '$Trace#setMetric',
       <String, dynamic>{'name': name, 'value': value},
     );
   }
diff --git a/packages/firebase_performance/test/firebase_performance_test.dart b/packages/firebase_performance/test/firebase_performance_test.dart
index 2dd5fe122998..7ce36bb65294 100644
--- a/packages/firebase_performance/test/firebase_performance_test.dart
+++ b/packages/firebase_performance/test/firebase_performance_test.dart
@@ -160,7 +160,7 @@ void main() {
         final int increment = 3;
 
         testTrace.start();
-        testTrace.putMetric(name, value);
+        testTrace.setMetric(name, value);
         traceLog.clear();
 
         testTrace.incrementMetric(name, increment);

From 353641e9261dbc4aa4f4b6b65605636318aac6e1 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 24 Apr 2019 12:24:28 -0700
Subject: [PATCH 16/40] Change method name to setMetric

---
 .../flutter/plugins/firebaseperformance/FlutterTrace.java   | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index 9b3b4c8f58e2..e544ffbc8c77 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -40,8 +40,8 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
       case "Trace#stop":
         stop(result);
         break;
-      case "Trace#putMetric":
-        putMetric(call, result);
+      case "Trace#setMetric":
+        setMetric(call, result);
         break;
       case "Trace#incrementMetric":
         incrementMetric(call, result);
@@ -74,7 +74,7 @@ private void stop(MethodChannel.Result result) {
     result.success(null);
   }
 
-  private void putMetric(MethodCall call, MethodChannel.Result result) {
+  private void setMetric(MethodCall call, MethodChannel.Result result) {
     final String name = call.argument("name");
     final Number value = call.argument("value");
     trace.putMetric(name, value.longValue());

From 0295e2edbbbb0b1791105321ad3adf092051208d Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 24 Apr 2019 16:43:47 -0700
Subject: [PATCH 17/40] Start of perf iOS

---
 .../ios/Classes/FLTFirebasePerformance.m      | 55 +++++++++++++++++++
 .../ios/Classes/FirebasePerformancePlugin.h   | 13 +++++
 .../ios/Classes/FirebasePerformancePlugin.m   |  8 +--
 3 files changed, 72 insertions(+), 4 deletions(-)
 create mode 100644 packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
new file mode 100644
index 000000000000..53f7bf3989c9
--- /dev/null
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -0,0 +1,55 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "FirebasePerformancePlugin.h"
+
+@interface FLTFirebasePerformance ()
+@property id<FlutterBinaryMessenger> binaryMessenger;
+@end
+
+@implementation FLTFirebasePerformance
++ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
+
+- (instancetype _Nonnull)initWithMessenger:(NSObject<FlutterBinaryMessenger> *_Nonnull)messenger {
+  self = [self init];
+  if (self) {
+    _binaryMessenger = messenger;
+  }
+
+  return self;
+}
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    if (![FIRApp appNamed:@"__FIRAPP_DEFAULT"]) {
+      NSLog(@"Configuring the default Firebase app...");
+      [FIRApp configure];
+      NSLog(@"Configured the default Firebase app %@.", [FIRApp defaultApp].name);
+    }
+  }
+
+  return self;
+}
+
+- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
+  if ([@"FirebasePerformance#isPerformanceCollectionEnabled" isEqualToString:call.method]) {
+    result(@([[FIRPerformance sharedInstance] isDataCollectionEnabled]));
+  } else if ([@"FirebasePerformance#setPerformanceCollectionEnabled" isEqualToString:call.method]) {
+    NSNumber *enable = call.arguments;
+    [[FIRPerformance sharedInstance] setDataCollectionEnabled:[enable boolValue]];
+    result(nil);
+  } else if ([@"Trace#start" isEqualToString:call.method]) {
+    [self handleTraceStart:call result:result];
+  } else if ([@"Trace#stop" isEqualToString:call.method]) {
+    [self handleTraceStop:call result:result];
+  } else if ([@"HttpMetric#start" isEqualToString:call.method]) {
+    [self handleHttpMetricStart:call result:result];
+  } else if ([@"HttpMetric#stop" isEqualToString:call.method]) {
+    [self handleHttpMetricStop:call result:result];
+  } else {
+    result(FlutterMethodNotImplemented);
+  }
+}
+@end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index d71c5351ac8d..ddc56dc80188 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -1,4 +1,17 @@
+#import <Firebase/Firebase.h>
 #import <Flutter/Flutter.h>
 
 @interface FLTFirebasePerformancePlugin : NSObject <FlutterPlugin>
 @end
+
+@interface FLTFirebasePerformance : NSObject<FlutterPlugin>
+- (instancetype _Nonnull)initWithMessenger:(NSObject<FlutterBinaryMessenger> *_Nonnull)messenger;
+@end
+
+@interface FLTTrace : NSObject<FlutterPlugin>
+- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
+@end
+
+@interface FLTHttpMetric : NSObject<FlutterPlugin>
+- (instancetype _Nonnull)initWithHttpMetric:(FIRHTTPMetric *_Nonnull)metric;
+@end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index 25073643815e..4a635b771ea9 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -4,8 +4,6 @@
 
 #import "FirebasePerformancePlugin.h"
 
-#import <Firebase/Firebase.h>
-
 @interface FLTFirebasePerformancePlugin ()
 @property(nonatomic, retain) NSMutableDictionary *traces;
 @property(nonatomic, retain) NSMutableDictionary *httpMetrics;
@@ -37,6 +35,7 @@ - (instancetype)init {
 }
 
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
+  /*
   if ([@"FirebasePerformance#isPerformanceCollectionEnabled" isEqualToString:call.method]) {
     result(@([[FIRPerformance sharedInstance] isDataCollectionEnabled]));
   } else if ([@"FirebasePerformance#setPerformanceCollectionEnabled" isEqualToString:call.method]) {
@@ -54,8 +53,9 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
   } else {
     result(FlutterMethodNotImplemented);
   }
+   */
 }
-
+/*
 - (void)handleTraceStart:(FlutterMethodCall *)call result:(FlutterResult)result {
   NSNumber *handle = call.arguments[@"handle"];
   NSString *name = call.arguments[@"name"];
@@ -156,5 +156,5 @@ - (void)handleHttpMetricStop:(FlutterMethodCall *)call result:(FlutterResult)res
   [_httpMetrics removeObjectForKey:handle];
   result(nil);
 }
-
+*/
 @end

From f581dd91b9aff0a3ea84a8d96d3c09c72eab3f90 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Thu, 25 Apr 2019 14:55:39 -0700
Subject: [PATCH 18/40] Firebase Performance iOS finish

---
 .../ios/Classes/FLTFirebasePerformance.m      |  98 ++++++++++--
 .../ios/Classes/FLTHttpMetric.m               | 116 ++++++++++++++
 .../ios/Classes/FLTTrace.m                    | 103 ++++++++++++
 .../ios/Classes/FirebasePerformancePlugin.h   |  10 +-
 .../ios/Classes/FirebasePerformancePlugin.m   | 148 +-----------------
 5 files changed, 311 insertions(+), 164 deletions(-)
 create mode 100644 packages/firebase_performance/ios/Classes/FLTHttpMetric.m
 create mode 100644 packages/firebase_performance/ios/Classes/FLTTrace.m

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
index 53f7bf3989c9..62879def378f 100644
--- a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -1,20 +1,22 @@
-// Copyright 2018 The Chromium Authors. All rights reserved.
+// Copyright 2019 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "FirebasePerformancePlugin.h"
 
 @interface FLTFirebasePerformance ()
-@property id<FlutterBinaryMessenger> binaryMessenger;
+@property id<FlutterPluginRegistrar> registrar;
+@property FIRPerformance *performance;
 @end
 
 @implementation FLTFirebasePerformance
 + (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
 
-- (instancetype _Nonnull)initWithMessenger:(NSObject<FlutterBinaryMessenger> *_Nonnull)messenger {
+- (instancetype _Nonnull)initWithRegistrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar {
   self = [self init];
   if (self) {
-    _binaryMessenger = messenger;
+    _performance = [FIRPerformance sharedInstance];
+    _registrar = registrar;
   }
 
   return self;
@@ -35,21 +37,85 @@ - (instancetype)init {
 
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
   if ([@"FirebasePerformance#isPerformanceCollectionEnabled" isEqualToString:call.method]) {
-    result(@([[FIRPerformance sharedInstance] isDataCollectionEnabled]));
+    [self isPerformanceCollectionEnabled:result];
   } else if ([@"FirebasePerformance#setPerformanceCollectionEnabled" isEqualToString:call.method]) {
-    NSNumber *enable = call.arguments;
-    [[FIRPerformance sharedInstance] setDataCollectionEnabled:[enable boolValue]];
-    result(nil);
-  } else if ([@"Trace#start" isEqualToString:call.method]) {
-    [self handleTraceStart:call result:result];
-  } else if ([@"Trace#stop" isEqualToString:call.method]) {
-    [self handleTraceStop:call result:result];
-  } else if ([@"HttpMetric#start" isEqualToString:call.method]) {
-    [self handleHttpMetricStart:call result:result];
-  } else if ([@"HttpMetric#stop" isEqualToString:call.method]) {
-    [self handleHttpMetricStop:call result:result];
+    [self setPerformanceCollectionEnabled:call result:result];
+  } else if ([@"FirebasePerformance#newTrace" isEqualToString:call.method]) {
+    [self newTrace:call result:result];
+  } else if ([@"FirebasePerformance#newHttpMetric" isEqualToString:call.method]) {
+    [self newHttpMetric:call result:result];
   } else {
     result(FlutterMethodNotImplemented);
   }
 }
+
+- (void)isPerformanceCollectionEnabled:(FlutterResult)result {
+  result(@([_performance isDataCollectionEnabled]));
+}
+
+- (void)setPerformanceCollectionEnabled:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSNumber *enable = call.arguments;
+  [_performance setDataCollectionEnabled:[enable boolValue]];
+  result(nil);
+}
+
+- (void)newTrace:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *traceName = call.arguments[@"traceName"];
+  FIRTrace *trace = [_performance traceWithName:traceName];
+
+  NSString *channelName = call.arguments[@"channelName"];
+  FlutterMethodChannel* channel = [FlutterMethodChannel
+                                   methodChannelWithName:channelName
+                                   binaryMessenger:[_registrar messenger]];
+
+  FLTTrace *delegate = [[FLTTrace alloc] initWithTrace:trace registrar:_registrar channel:channel];
+  [_registrar addMethodCallDelegate:delegate channel:channel];
+  result(nil);
+}
+
+- (void)newHttpMetric:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *httpMethod = call.arguments[@"httpMethod"];
+  FIRHTTPMethod method = [FLTFirebasePerformance parseHttpMethod:httpMethod];
+
+  NSString *urlString = call.arguments[@"url"];
+  NSURL *url = [NSURL URLWithString:urlString];
+
+  FIRHTTPMetric *metric = [[FIRHTTPMetric alloc] initWithURL:url HTTPMethod:method];
+
+  NSString *channelName = call.arguments[@"channelName"];
+  FlutterMethodChannel *channel = [FlutterMethodChannel
+                                   methodChannelWithName:channelName
+                                   binaryMessenger:[_registrar messenger]];
+
+  FLTHttpMetric *delegate = [[FLTHttpMetric alloc] initWithHTTPMetric:metric
+                                                            registrar:_registrar
+                                                              channel:channel];
+  [_registrar addMethodCallDelegate:delegate channel:channel];
+  result(nil);
+}
+
++ (FIRHTTPMethod)parseHttpMethod:(NSString *)method {
+  if ([@"HttpMethod.Connect" isEqualToString:method]) {
+    return FIRHTTPMethodCONNECT;
+  } else if ([@"HttpMethod.Delete" isEqualToString:method]) {
+    return FIRHTTPMethodDELETE;
+  } else if ([@"HttpMethod.Get" isEqualToString:method]) {
+    return FIRHTTPMethodGET;
+  } else if ([@"HttpMethod.Head" isEqualToString:method]) {
+    return FIRHTTPMethodHEAD;
+  } else if ([@"HttpMethod.Options" isEqualToString:method]) {
+    return FIRHTTPMethodOPTIONS;
+  } else if ([@"HttpMethod.Patch" isEqualToString:method]) {
+    return FIRHTTPMethodPATCH;
+  } else if ([@"HttpMethod.Post" isEqualToString:method]) {
+    return FIRHTTPMethodPOST;
+  } else if ([@"HttpMethod.Put" isEqualToString:method]) {
+    return FIRHTTPMethodPUT;
+  } else if ([@"HttpMethod.Trace" isEqualToString:method]) {
+    return FIRHTTPMethodTRACE;
+  }
+
+  NSString *reason = [NSString stringWithFormat:@"Invalid HttpMethod: %@", method];
+  @throw [[NSException alloc] initWithName:NSInvalidArgumentException reason:reason userInfo:nil];
+}
 @end
diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
new file mode 100644
index 000000000000..5d6ca4df6552
--- /dev/null
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -0,0 +1,116 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "FirebasePerformancePlugin.h"
+
+@interface FLTHttpMetric ()
+@property FIRHTTPMetric *metric;
+@property id<FlutterPluginRegistrar> registrar;
+@property FlutterMethodChannel *channel;
+@end
+
+@implementation FLTHttpMetric
++ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
+
+- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *)metric
+                                  registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
+                                    channel:(FlutterMethodChannel *)channel {
+  self = [self init];
+  if (self) {
+    _metric = metric;
+    _registrar = registrar;
+    _channel = channel;
+  }
+
+  return self;
+}
+
+- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
+  if ([@"HttpMetric#start" isEqualToString:call.method]) {
+    [self start:result];
+  } else if ([@"HttpMetric#stop" isEqualToString:call.method]) {
+    [self stop:result];
+  } else if ([@"HttpMetric#httpResponseCode" isEqualToString:call.method]) {
+    [self setHttpResponseCode:call result:result];
+  } else if ([@"HttpMetric#requestPayloadSize" isEqualToString:call.method]) {
+    [self requestPayloadSize:call result:result];
+  } else if ([@"HttpMetric#responseContentType" isEqualToString:call.method]) {
+    [self responseContentType:call result:result];
+  } else if ([@"HttpMetric#responsePayloadSize" isEqualToString:call.method]) {
+    [self responsePayloadSize:call result:result];
+  } else if ([@"HttpMetric#putAttribute" isEqualToString:call.method]) {
+    [self putAttribute:call result:result];
+  } else if ([@"HttpMetric#removeAttribute" isEqualToString:call.method]) {
+    [self removeAttribute:call result:result];
+  } else if ([@"HttpMetric#getAttributes" isEqualToString:call.method]) {
+    [self getAttributes:result];
+  } else {
+    result(FlutterMethodNotImplemented);
+  }
+}
+
+- (void)start:(FlutterResult)result {
+  [_metric start];
+  result(nil);
+}
+
+- (void)stop:(FlutterResult)result {
+  [_metric stop];
+  [_registrar addMethodCallDelegate:nil channel:nil];
+  result(nil);
+}
+
+- (void)setHttpResponseCode:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSNumber *responseCode = call.arguments[@"httpResponseCode"];
+
+  if (![responseCode isEqual:[NSNull null]]) _metric.responseCode = [responseCode integerValue];
+  result(nil);
+}
+
+- (void)requestPayloadSize:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSNumber *requestPayloadSize = call.arguments[@"requestPayloadSize"];
+
+  if (![requestPayloadSize isEqual:[NSNull null]]) {
+    _metric.requestPayloadSize = [requestPayloadSize longValue];
+  }
+  result(nil);
+}
+
+- (void)responseContentType:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *responseContentType = call.arguments[@"responseContentType"];
+
+  if (![responseContentType isEqual:[NSNull null]]) {
+    _metric.responseContentType = responseContentType;
+  }
+  result(nil);
+}
+
+- (void)responsePayloadSize:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSNumber *responsePayloadSize = call.arguments[@"responsePayloadSize"];
+
+  if (![responsePayloadSize isEqual:[NSNull null]]) {
+    _metric.responsePayloadSize = [responsePayloadSize longValue];
+  }
+  result(nil);
+}
+
+- (void)putAttribute:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+  NSString *value = call.arguments[@"value"];
+
+  [_metric setValue:value forAttribute:name];
+  result(nil);
+}
+
+- (void)removeAttribute:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+
+  [_metric removeAttribute:name];
+  result(nil);
+}
+
+- (void)getAttributes:(FlutterResult)result {
+  result(_metric.attributes);
+}
+@end
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
new file mode 100644
index 000000000000..72e94a17638c
--- /dev/null
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -0,0 +1,103 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "FirebasePerformancePlugin.h"
+
+@interface FLTTrace ()
+@property FIRTrace *trace;
+@property id<FlutterPluginRegistrar> registrar;
+@property FlutterMethodChannel *channel;
+@end
+
+@implementation FLTTrace
++ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
+
+- (instancetype _Nonnull)initWithTrace:(FIRTrace *)trace
+                             registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
+                               channel:(FlutterMethodChannel *)channel {
+  self = [self init];
+  if (self) {
+    _registrar = registrar;
+    _channel = channel;
+    _trace = trace;
+  }
+
+  return self;
+}
+
+- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
+  if ([@"Trace#start" isEqualToString:call.method]) {
+    [self start:result];
+  } else if ([@"Trace#stop" isEqualToString:call.method]) {
+    [self stop:result];
+  } else if ([@"Trace#setMetric" isEqualToString:call.method]) {
+    [self setMetric:call result:result];
+  } else if ([@"Trace#incrementMetric" isEqualToString:call.method]) {
+    [self incrementMetric:call result:result];
+  } else if ([@"Trace#getMetric" isEqualToString:call.method]) {
+    [self getMetric:call result:result];
+  } else if ([@"Trace#putAttribute" isEqualToString:call.method]) {
+    [self putAttribute:call result:result];
+  } else if ([@"Trace#removeAttribute" isEqualToString:call.method]) {
+    [self removeAttribute:call result:result];
+  } else if ([@"Trace#getAttributes" isEqualToString:call.method]) {
+    [self getAttributes:result];
+  } else {
+    result(FlutterMethodNotImplemented);
+  }
+}
+
+- (void)start:(FlutterResult)result {
+  [_trace start];
+  result(nil);
+}
+
+- (void)stop:(FlutterResult)result {
+  [_trace stop];
+  [_registrar addMethodCallDelegate:nil channel:_channel];
+  result(nil);
+}
+
+- (void)setMetric:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+  NSNumber *value = call.arguments[@"value"];
+
+  [_trace setIntValue:value.longValue forMetric:name];
+  result(nil);
+}
+
+- (void)incrementMetric:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+  NSNumber *value = call.arguments[@"value"];
+
+  [_trace incrementMetric:name byInt:value.longValue];
+  result(nil);
+}
+
+- (void)getMetric:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+
+  int64_t metric = [_trace valueForIntMetric:name];
+  result(@(metric));
+}
+
+- (void)putAttribute:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+  NSString *value = call.arguments[@"value"];
+
+  [_trace setValue:value forAttribute:name];
+  result(nil);
+}
+
+- (void)removeAttribute:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString *name = call.arguments[@"name"];
+
+  [_trace removeAttribute:name];
+  result(nil);
+}
+
+- (void)getAttributes:(FlutterResult)result {
+  result(_trace.attributes);
+}
+@end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index ddc56dc80188..8eda01fb8dad 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -5,13 +5,17 @@
 @end
 
 @interface FLTFirebasePerformance : NSObject<FlutterPlugin>
-- (instancetype _Nonnull)initWithMessenger:(NSObject<FlutterBinaryMessenger> *_Nonnull)messenger;
+- (instancetype _Nonnull)initWithRegistrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar;
 @end
 
 @interface FLTTrace : NSObject<FlutterPlugin>
-- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
+- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace
+                             registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
+                               channel:(FlutterMethodChannel *_Nonnull)channel;
 @end
 
 @interface FLTHttpMetric : NSObject<FlutterPlugin>
-- (instancetype _Nonnull)initWithHttpMetric:(FIRHTTPMetric *_Nonnull)metric;
+- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric
+                                  registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
+                                    channel:(FlutterMethodChannel *_Nonnull)channel;
 @end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index 4a635b771ea9..e96ef47e288a 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -4,157 +4,15 @@
 
 #import "FirebasePerformancePlugin.h"
 
-@interface FLTFirebasePerformancePlugin ()
-@property(nonatomic, retain) NSMutableDictionary *traces;
-@property(nonatomic, retain) NSMutableDictionary *httpMetrics;
-@end
-
 @implementation FLTFirebasePerformancePlugin
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   FlutterMethodChannel *channel =
       [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/firebase_performance"
                                   binaryMessenger:[registrar messenger]];
-  FLTFirebasePerformancePlugin *instance = [[FLTFirebasePerformancePlugin alloc] init];
-  [registrar addMethodCallDelegate:instance channel:channel];
-}
-
-- (instancetype)init {
-  self = [super init];
-  if (self) {
-    if (![FIRApp appNamed:@"__FIRAPP_DEFAULT"]) {
-      NSLog(@"Configuring the default Firebase app...");
-      [FIRApp configure];
-      NSLog(@"Configured the default Firebase app %@.", [FIRApp defaultApp].name);
-    }
-
-    _traces = [[NSMutableDictionary alloc] init];
-    _httpMetrics = [[NSMutableDictionary alloc] init];
-  }
-
-  return self;
-}
-
-- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
-  /*
-  if ([@"FirebasePerformance#isPerformanceCollectionEnabled" isEqualToString:call.method]) {
-    result(@([[FIRPerformance sharedInstance] isDataCollectionEnabled]));
-  } else if ([@"FirebasePerformance#setPerformanceCollectionEnabled" isEqualToString:call.method]) {
-    NSNumber *enable = call.arguments;
-    [[FIRPerformance sharedInstance] setDataCollectionEnabled:[enable boolValue]];
-    result(nil);
-  } else if ([@"Trace#start" isEqualToString:call.method]) {
-    [self handleTraceStart:call result:result];
-  } else if ([@"Trace#stop" isEqualToString:call.method]) {
-    [self handleTraceStop:call result:result];
-  } else if ([@"HttpMetric#start" isEqualToString:call.method]) {
-    [self handleHttpMetricStart:call result:result];
-  } else if ([@"HttpMetric#stop" isEqualToString:call.method]) {
-    [self handleHttpMetricStop:call result:result];
-  } else {
-    result(FlutterMethodNotImplemented);
-  }
-   */
-}
-/*
-- (void)handleTraceStart:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSNumber *handle = call.arguments[@"handle"];
-  NSString *name = call.arguments[@"name"];
-
-  FIRTrace *trace = [[FIRPerformance sharedInstance] traceWithName:name];
-  [_traces setObject:trace forKey:handle];
-  [trace start];
-  result(nil);
-}
-
-- (void)handleTraceStop:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSNumber *handle = call.arguments[@"handle"];
-  FIRTrace *trace = [_traces objectForKey:handle];
 
-  NSDictionary *metrics = call.arguments[@"metrics"];
-  [metrics enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSNumber *value, BOOL *stop) {
-    [trace setIntValue:[value longLongValue] forMetric:key];
-  }];
-
-  NSDictionary *attributes = call.arguments[@"attributes"];
-  [attributes enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *value, BOOL *stop) {
-    [trace setValue:value forAttribute:key];
-  }];
-
-  [trace stop];
-  [_traces removeObjectForKey:handle];
-  result(nil);
-}
-
-- (void)handleHttpMetricStart:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSNumber *handle = call.arguments[@"handle"];
-  NSURL *url = [NSURL URLWithString:call.arguments[@"url"]];
-
-  NSNumber *httpMethod = call.arguments[@"httpMethod"];
-  FIRHTTPMethod method;
-  switch ([httpMethod intValue]) {
-    case 0:
-      method = FIRHTTPMethodCONNECT;
-      break;
-    case 1:
-      method = FIRHTTPMethodDELETE;
-      break;
-    case 2:
-      method = FIRHTTPMethodGET;
-      break;
-    case 3:
-      method = FIRHTTPMethodHEAD;
-      break;
-    case 4:
-      method = FIRHTTPMethodOPTIONS;
-      break;
-    case 5:
-      method = FIRHTTPMethodPATCH;
-      break;
-    case 6:
-      method = FIRHTTPMethodPOST;
-      break;
-    case 7:
-      method = FIRHTTPMethodPUT;
-      break;
-    case 8:
-      method = FIRHTTPMethodTRACE;
-      break;
-    default:
-      method = [httpMethod intValue];
-      break;
-  }
-
-  FIRHTTPMetric *metric = [[FIRHTTPMetric alloc] initWithURL:url HTTPMethod:method];
-  [_httpMetrics setObject:metric forKey:handle];
-  [metric start];
-  result(nil);
+  FLTFirebasePerformance *instance = [[FLTFirebasePerformance alloc] initWithRegistrar:registrar];
+  [registrar addMethodCallDelegate:instance channel:channel];
 }
 
-- (void)handleHttpMetricStop:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSNumber *handle = call.arguments[@"handle"];
-  FIRHTTPMetric *metric = [_httpMetrics objectForKey:handle];
-
-  NSNumber *responseCode = call.arguments[@"httpResponseCode"];
-  NSNumber *requestPayloadSize = call.arguments[@"requestPayloadSize"];
-  NSString *responseContentType = call.arguments[@"responseContentType"];
-  NSNumber *responsePayloadSize = call.arguments[@"responsePayloadSize"];
-
-  if (![responseCode isEqual:[NSNull null]]) metric.responseCode = [responseCode integerValue];
-  if (![requestPayloadSize isEqual:[NSNull null]])
-    metric.requestPayloadSize = [requestPayloadSize longValue];
-  if (![responseContentType isEqual:[NSNull null]])
-    metric.responseContentType = responseContentType;
-  if (![responsePayloadSize isEqual:[NSNull null]])
-    metric.responsePayloadSize = [responsePayloadSize longValue];
-
-  NSDictionary *attributes = call.arguments[@"attributes"];
-  [attributes enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *value, BOOL *stop) {
-    [metric setValue:value forAttribute:key];
-  }];
-
-  [metric stop];
-  [_httpMetrics removeObjectForKey:handle];
-  result(nil);
-}
-*/
+- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {}
 @end

From c07c810b6b5d309ead8d0c96ce951c7df6fa131f Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 29 Apr 2019 21:58:19 -0700
Subject: [PATCH 19/40] Redesign of flutter plugin objects

---
 .../FirebasePerformancePlugin.java            | 52 +++++++++++++++-
 .../FlutterFirebasePerformance.java           | 59 ++++++++++++++++---
 .../FlutterHttpMetric.java                    | 54 +++--------------
 .../firebaseperformance/FlutterTrace.java     | 28 +++------
 4 files changed, 117 insertions(+), 76 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
index ad115a499d2f..11748c4162bc 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
@@ -4,15 +4,63 @@
 
 package io.flutter.plugins.firebaseperformance;
 
+import android.util.SparseArray;
+import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
 
 /** FirebasePerformancePlugin */
-public class FirebasePerformancePlugin {
+public class FirebasePerformancePlugin implements MethodChannel.MethodCallHandler {
   private static final String CHANNEL_NAME = "plugins.flutter.io/firebase_performance";
 
+  private static final SparseArray<MethodChannel.MethodCallHandler> handlers = new SparseArray<>();
+
   public static void registerWith(Registrar registrar) {
     final MethodChannel channel = new MethodChannel(registrar.messenger(), CHANNEL_NAME);
-    channel.setMethodCallHandler(FlutterFirebasePerformance.getInstance(registrar.messenger()));
+    channel.setMethodCallHandler(new FirebasePerformancePlugin());
+  }
+
+  @Override
+  public void onMethodCall(MethodCall call, MethodChannel.Result result) {
+    switch (call.method) {
+      case "FirebasePerformance#instance":
+        FlutterFirebasePerformance.getInstance(call, result);
+        break;
+      case "FirebasePerformance#isPerformanceCollectionEnabled":
+      case "FirebasePerformance#setPerformanceCollectionEnabled":
+      case "FirebasePerformance#newTrace":
+      case "FirebasePerformance#newHttpMetric":
+      case "Trace#start":
+      case "Trace#stop":
+      case "Trace#setMetric":
+      case "Trace#incrementMetric":
+      case "Trace#getMetric":
+      case "PerformanceAttributes#putAttribute":
+      case "PerformanceAttributes#removeAttribute":
+      case "PerformanceAttributes#getAttributes":
+        getHandler(call).onMethodCall(call, result);
+        break;
+      default:
+        result.notImplemented();
+    }
+  }
+
+  static void addHandler(final int handle, final MethodChannel.MethodCallHandler handler) {
+    if (handlers.get(handle) != null) {
+      final String message = String.format("Object for handle already exists: %s", handle);
+      throw new IllegalArgumentException(message);
+    }
+
+    handlers.put(handle, handler);
+  }
+
+  static void removeHandler(final int handle) {
+    handlers.remove(handle);
+  }
+
+  @SuppressWarnings("ConstantConditions")
+  private static MethodChannel.MethodCallHandler getHandler(final MethodCall call) {
+    final Integer handle = call.argument("handle");
+    return handlers.get(handle);
   }
 }
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
index 9e66cf732f50..312363fd46e7 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
@@ -5,20 +5,47 @@
 package io.flutter.plugins.firebaseperformance;
 
 import com.google.firebase.perf.FirebasePerformance;
-import io.flutter.plugin.common.BinaryMessenger;
+import com.google.firebase.perf.metrics.HttpMetric;
+import com.google.firebase.perf.metrics.Trace;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 
 public class FlutterFirebasePerformance implements MethodChannel.MethodCallHandler {
-  private final BinaryMessenger binaryMessenger;
+  private static String parseHttpMethod(String httpMethod) {
+    switch (httpMethod) {
+      case "HttpMethod.Connect":
+        return FirebasePerformance.HttpMethod.CONNECT;
+      case "HttpMethod.Delete":
+        return FirebasePerformance.HttpMethod.DELETE;
+      case "HttpMethod.Get":
+        return FirebasePerformance.HttpMethod.GET;
+      case "HttpMethod.Head":
+        return FirebasePerformance.HttpMethod.HEAD;
+      case "HttpMethod.Options":
+        return FirebasePerformance.HttpMethod.OPTIONS;
+      case "HttpMethod.Patch":
+        return FirebasePerformance.HttpMethod.PATCH;
+      case "HttpMethod.Post":
+        return FirebasePerformance.HttpMethod.POST;
+      case "HttpMethod.Put":
+        return FirebasePerformance.HttpMethod.PUT;
+      case "HttpMethod.Trace":
+        return FirebasePerformance.HttpMethod.TRACE;
+      default:
+        throw new IllegalArgumentException(String.format("No HttpMethod for: %s", httpMethod));
+    }
+  }
+
   private final FirebasePerformance performance;
 
-  static FlutterFirebasePerformance getInstance(BinaryMessenger messenger) {
-    return new FlutterFirebasePerformance(messenger);
+  @SuppressWarnings("ConstantConditions")
+  static void getInstance(MethodCall call, MethodChannel.Result result) {
+    final Integer handle = call.argument("handle");
+    FirebasePerformancePlugin.addHandler(handle, new FlutterFirebasePerformance());
+    result.success(null);
   }
 
-  private FlutterFirebasePerformance(BinaryMessenger messenger) {
-    this.binaryMessenger = messenger;
+  private FlutterFirebasePerformance() {
     this.performance = FirebasePerformance.getInstance();
   }
 
@@ -52,11 +79,27 @@ private void setPerformanceCollectionEnabled(MethodCall call, MethodChannel.Resu
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void newTrace(MethodCall call, MethodChannel.Result result) {
-    new FlutterTrace(performance, binaryMessenger, call, result);
+    final String name = call.argument("name");
+    final Trace trace = performance.newTrace(name);
+
+    final Integer handle = call.argument("handle");
+    FirebasePerformancePlugin.addHandler(handle, new FlutterTrace(trace));
+
+    result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void newHttpMetric(MethodCall call, MethodChannel.Result result) {
-    new FlutterHttpMetric(performance, binaryMessenger, call, result);
+    final String url = call.argument("url");
+    final String httpMethod = call.argument("httpMethod");
+
+    final HttpMetric metric = performance.newHttpMetric(url, parseHttpMethod(httpMethod));
+
+    final Integer handle = call.argument("handle");
+    FirebasePerformancePlugin.addHandler(handle, new FlutterHttpMetric(metric));
+
+    result.success(null);
   }
 }
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index 927a94719fea..0fdc99998af4 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -4,57 +4,16 @@
 
 package io.flutter.plugins.firebaseperformance;
 
-import com.google.firebase.perf.FirebasePerformance;
 import com.google.firebase.perf.metrics.HttpMetric;
-import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 
 @SuppressWarnings("ConstantConditions")
 public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
-  private static String parseHttpMethod(String httpMethod) {
-    switch (httpMethod) {
-      case "HttpMethod.Connect":
-        return FirebasePerformance.HttpMethod.CONNECT;
-      case "HttpMethod.Delete":
-        return FirebasePerformance.HttpMethod.DELETE;
-      case "HttpMethod.Get":
-        return FirebasePerformance.HttpMethod.GET;
-      case "HttpMethod.Head":
-        return FirebasePerformance.HttpMethod.HEAD;
-      case "HttpMethod.Options":
-        return FirebasePerformance.HttpMethod.OPTIONS;
-      case "HttpMethod.Patch":
-        return FirebasePerformance.HttpMethod.PATCH;
-      case "HttpMethod.Post":
-        return FirebasePerformance.HttpMethod.POST;
-      case "HttpMethod.Put":
-        return FirebasePerformance.HttpMethod.PUT;
-      case "HttpMethod.Trace":
-        return FirebasePerformance.HttpMethod.TRACE;
-      default:
-        throw new IllegalArgumentException(String.format("No HttpMethod for: %s", httpMethod));
-    }
-  }
-
   private final HttpMetric httpMetric;
-  private final MethodChannel channel;
-
-  FlutterHttpMetric(
-      FirebasePerformance performance,
-      BinaryMessenger messenger,
-      MethodCall call,
-      MethodChannel.Result result) {
-    final String channelName = call.argument("channelName");
-    final String url = call.argument("url");
-    final String httpMethod = call.argument("httpMethod");
 
-    this.httpMetric = performance.newHttpMetric(url, parseHttpMethod(httpMethod));
-
-    this.channel = new MethodChannel(messenger, channelName);
-    channel.setMethodCallHandler(this);
-
-    result.success(null);
+  FlutterHttpMetric(final HttpMetric metric) {
+    this.httpMetric = metric;
   }
 
   @Override
@@ -64,7 +23,7 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
         start(result);
         break;
       case "HttpMetric#stop":
-        stop(result);
+        stop(call, result);
         break;
       case "HttpMetric#httpResponseCode":
         setHttpResponseCode(call, result);
@@ -97,9 +56,12 @@ private void start(MethodChannel.Result result) {
     result.success(null);
   }
 
-  private void stop(MethodChannel.Result result) {
+  private void stop(MethodCall call, MethodChannel.Result result) {
     httpMetric.stop();
-    channel.setMethodCallHandler(null);
+
+    final Integer handle = call.argument("handle");
+    FirebasePerformancePlugin.removeHandler(handle);
+
     result.success(null);
   }
 
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index e544ffbc8c77..63a469cdcd2f 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -4,31 +4,16 @@
 
 package io.flutter.plugins.firebaseperformance;
 
-import com.google.firebase.perf.FirebasePerformance;
 import com.google.firebase.perf.metrics.Trace;
-import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 
 @SuppressWarnings("ConstantConditions")
 public class FlutterTrace implements MethodChannel.MethodCallHandler {
   private final Trace trace;
-  private final MethodChannel channel;
 
-  FlutterTrace(
-      FirebasePerformance performance,
-      BinaryMessenger messenger,
-      MethodCall call,
-      MethodChannel.Result result) {
-    final String traceName = call.argument("traceName");
-    final String channelName = call.argument("channelName");
-
-    this.trace = performance.newTrace(traceName);
-
-    this.channel = new MethodChannel(messenger, channelName);
-    channel.setMethodCallHandler(this);
-
-    result.success(null);
+  FlutterTrace(final Trace trace) {
+    this.trace = trace;
   }
 
   @Override
@@ -38,7 +23,7 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
         start(result);
         break;
       case "Trace#stop":
-        stop(result);
+        stop(call, result);
         break;
       case "Trace#setMetric":
         setMetric(call, result);
@@ -68,9 +53,12 @@ private void start(MethodChannel.Result result) {
     result.success(null);
   }
 
-  private void stop(MethodChannel.Result result) {
+  private void stop(MethodCall call, MethodChannel.Result result) {
     trace.stop();
-    channel.setMethodCallHandler(null);
+
+    final Integer handle = call.argument("handle");
+    FirebasePerformancePlugin.removeHandler(handle);
+
     result.success(null);
   }
 

From 7800e5d0d616ca971089598bd49b6827eb745fd3 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 29 Apr 2019 22:41:17 -0700
Subject: [PATCH 20/40] 3rd redesign :(

---
 .../lib/src/firebase_performance.dart         | 40 +++++++++-------
 .../lib/src/http_metric.dart                  | 46 +++++++++++++------
 .../lib/src/performance_attributes.dart       | 18 +++++---
 .../firebase_performance/lib/src/trace.dart   | 27 ++++++-----
 4 files changed, 83 insertions(+), 48 deletions(-)

diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index 571e6b8063bd..e2498ec172cb 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -11,16 +11,24 @@ enum HttpMethod { Connect, Delete, Get, Head, Options, Patch, Post, Put, Trace }
 ///
 /// You can get an instance by calling [FirebasePerformance.instance].
 class FirebasePerformance {
-  FirebasePerformance._();
+  FirebasePerformance._(this._handle) {
+    channel.invokeMethod<bool>(
+      'FirebasePerformance#instance',
+      <String, dynamic>{'handle': _handle},
+    );
+  }
+
+  static int _nextHandle = 0;
+
+  final int _handle;
 
   @visibleForTesting
   static const MethodChannel channel =
       MethodChannel('plugins.flutter.io/firebase_performance');
 
   /// Singleton of [FirebasePerformance].
-  static final FirebasePerformance instance = FirebasePerformance._();
-
-  static int _channelCount = 0;
+  static final FirebasePerformance instance =
+      FirebasePerformance._(_nextHandle++);
 
   /// Determines whether performance monitoring is enabled or disabled.
   ///
@@ -29,7 +37,8 @@ class FirebasePerformance {
   /// does not reflect whether instrumentation is enabled/disabled.
   Future<bool> isPerformanceCollectionEnabled() {
     return channel.invokeMethod<bool>(
-      'FirebasePerformance#isPerformanceCollectionEnabled',
+      '$FirebasePerformance#isPerformanceCollectionEnabled',
+      <String, dynamic>{'handle': _handle},
     );
   }
 
@@ -39,8 +48,8 @@ class FirebasePerformance {
   /// application. By default, performance monitoring is enabled.
   Future<void> setPerformanceCollectionEnabled(bool enable) {
     return channel.invokeMethod<void>(
-      'FirebasePerformance#setPerformanceCollectionEnabled',
-      enable,
+      '$FirebasePerformance#setPerformanceCollectionEnabled',
+      <String, dynamic>{'handle': _handle, 'enable': enable},
     );
   }
 
@@ -50,34 +59,31 @@ class FirebasePerformance {
   /// underscore _ character, and max length of [Trace.maxTraceNameLength]
   /// characters.
   Trace newTrace(String name) {
-    final String channelName =
-        '${FirebasePerformance.channel.name}/$Trace/${_channelCount++}';
+    final int handle = _nextHandle++;
 
     FirebasePerformance.channel.invokeMethod<void>(
       '$FirebasePerformance#newTrace',
-      <String, dynamic>{'channelName': channelName, 'traceName': name},
+      <String, dynamic>{'handle': _handle, 'traceHandle': handle, 'name': name},
     );
 
-    final MethodChannel channel = MethodChannel(channelName);
-    return Trace._(channel, name);
+    return Trace._(handle, name);
   }
 
   /// Creates [HttpMetric] for collecting performance for one request/response.
   HttpMetric newHttpMetric(String url, HttpMethod httpMethod) {
-    final String channelName =
-        '${FirebasePerformance.channel.name}/$HttpMetric/${_channelCount++}';
+    final int handle = _nextHandle++;
 
     FirebasePerformance.channel.invokeMethod<void>(
       '$FirebasePerformance#newHttpMetric',
       <String, dynamic>{
-        'channelName': channelName,
+        'handle': _handle,
+        'httpMetricHandle': handle,
         'url': url,
         'httpMethod': httpMethod.toString(),
       },
     );
 
-    final MethodChannel channel = MethodChannel(channelName);
-    return HttpMetric._(channel);
+    return HttpMetric._(handle, url, httpMethod);
   }
 
   /// Creates a [Trace] object with given [name] and starts the trace.
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index 12ec1dd895f8..a9f54830790b 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -16,7 +16,10 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class HttpMetric extends PerformanceAttributes {
-  HttpMetric._(this.channel);
+  HttpMetric._(this._handle, this.url, this.httpMethod);
+
+  final String url;
+  final HttpMethod httpMethod;
 
   @override
   bool _hasStarted = false;
@@ -29,9 +32,8 @@ class HttpMetric extends PerformanceAttributes {
   String _responseContentType;
   int _responsePayloadSize;
 
-  @visibleForTesting
   @override
-  final MethodChannel channel;
+  final int _handle;
 
   /// HttpResponse code of the request.
   int get httpResponseCode => _httpResponseCode;
@@ -53,9 +55,12 @@ class HttpMetric extends PerformanceAttributes {
     if (_hasStopped) return;
 
     _httpResponseCode = httpResponseCode;
-    channel.invokeMethod<void>(
+    FirebasePerformance.channel.invokeMethod<void>(
       '$HttpMetric#httpResponseCode',
-      httpResponseCode,
+      <String, dynamic>{
+        'handle': _handle,
+        'httpResponseCode': httpResponseCode,
+      },
     );
   }
 
@@ -67,9 +72,12 @@ class HttpMetric extends PerformanceAttributes {
     if (_hasStopped) return;
 
     _requestPayloadSize = requestPayloadSize;
-    channel.invokeMethod<void>(
+    FirebasePerformance.channel.invokeMethod<void>(
       '$HttpMetric#requestPayloadSize',
-      requestPayloadSize,
+      <String, dynamic>{
+        'handle': _handle,
+        'requestPayloadSize': requestPayloadSize,
+      },
     );
   }
 
@@ -81,9 +89,12 @@ class HttpMetric extends PerformanceAttributes {
     if (_hasStopped) return;
 
     _responseContentType = responseContentType;
-    channel.invokeMethod<void>(
+    FirebasePerformance.channel.invokeMethod<void>(
       '$HttpMetric#responseContentType',
-      responseContentType,
+      <String, dynamic>{
+        'handle': _handle,
+        'responseContentType': responseContentType,
+      },
     );
   }
 
@@ -95,9 +106,12 @@ class HttpMetric extends PerformanceAttributes {
     if (_hasStopped) return;
 
     _responsePayloadSize = responsePayloadSize;
-    channel.invokeMethod<void>(
+    FirebasePerformance.channel.invokeMethod<void>(
       '$HttpMetric#responsePayloadSize',
-      responsePayloadSize,
+      <String, dynamic>{
+        'handle': _handle,
+        'responsePayloadSize': responsePayloadSize,
+      },
     );
   }
 
@@ -111,7 +125,10 @@ class HttpMetric extends PerformanceAttributes {
     if (_hasStopped) return Future<void>.value(null);
 
     _hasStarted = true;
-    return channel.invokeMethod<void>('$HttpMetric#start');
+    return FirebasePerformance.channel.invokeMethod<void>(
+      '$HttpMetric#start',
+      <String, dynamic>{'handle': _handle},
+    );
   }
 
   /// Stops this [HttpMetric].
@@ -126,6 +143,9 @@ class HttpMetric extends PerformanceAttributes {
     if (_hasStopped) return Future<void>.value(null);
 
     _hasStopped = true;
-    return channel.invokeMethod<void>('$HttpMetric#stop');
+    return FirebasePerformance.channel.invokeMethod<void>(
+      '$HttpMetric#stop',
+      <String, dynamic>{'handle': _handle},
+    );
   }
 }
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index de2f6452c41d..c12abb499655 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -20,8 +20,7 @@ abstract class PerformanceAttributes {
   bool get _hasStarted;
   bool get _hasStopped;
 
-  @visibleForTesting
-  MethodChannel get channel;
+  int get _handle;
 
   /// Sets a String [value] for the specified [attribute].
   ///
@@ -42,9 +41,13 @@ abstract class PerformanceAttributes {
     }
 
     _attributes[attribute] = value;
-    return channel.invokeMethod<void>(
+    return FirebasePerformance.channel.invokeMethod<void>(
       '$PerformanceAttributes#putAttribute',
-      <String, String>{'attribute': attribute, 'value': value},
+      <String, dynamic>{
+        'handle': _handle,
+        'attribute': attribute,
+        'value': value,
+      },
     );
   }
 
@@ -53,9 +56,9 @@ abstract class PerformanceAttributes {
     if (!_hasStarted || _hasStopped) return Future<void>.value(null);
 
     _attributes.remove(attribute);
-    return channel.invokeMethod<void>(
+    return FirebasePerformance.channel.invokeMethod<void>(
       '$PerformanceAttributes#removeAttribute',
-      attribute,
+      <String, dynamic>{'handle': _handle, 'attribute': attribute},
     );
   }
 
@@ -67,8 +70,9 @@ abstract class PerformanceAttributes {
       ));
     }
 
-    return channel.invokeMapMethod<String, String>(
+    return FirebasePerformance.channel.invokeMapMethod<String, String>(
       '$PerformanceAttributes#getAttributes',
+      <String, dynamic>{'handle': _handle},
     );
   }
 }
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 20e240385eb7..5f8a98ad0151 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -19,7 +19,7 @@ part of firebase_performance;
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
 class Trace extends PerformanceAttributes {
-  Trace._(this.channel, this.name);
+  Trace._(this._handle, this.name);
 
   /// Maximum allowed length of the name of a [Trace].
   static const int maxTraceNameLength = 100;
@@ -32,9 +32,8 @@ class Trace extends PerformanceAttributes {
   @override
   bool _hasStopped = false;
 
-  @visibleForTesting
   @override
-  final MethodChannel channel;
+  final int _handle;
 
   /// Name representing this [Trace] on the Firebase Console.
   final String name;
@@ -49,7 +48,10 @@ class Trace extends PerformanceAttributes {
     if (_hasStopped) return Future<void>.value(null);
 
     _hasStarted = true;
-    return channel.invokeMethod<void>('$Trace#start');
+    return FirebasePerformance.channel.invokeMethod<void>(
+      '$Trace#start',
+      <String, dynamic>{'handle': _handle},
+    );
   }
 
   /// Stops this [Trace].
@@ -64,7 +66,10 @@ class Trace extends PerformanceAttributes {
     if (_hasStopped) return Future<void>.value(null);
 
     _hasStopped = true;
-    return channel.invokeMethod<void>('$Trace#stop');
+    return FirebasePerformance.channel.invokeMethod<void>(
+      '$Trace#stop',
+      <String, dynamic>{'handle': _handle},
+    );
   }
 
   /// Increments the metric with the given [name].
@@ -78,9 +83,9 @@ class Trace extends PerformanceAttributes {
     }
 
     _metrics[name] += value;
-    return channel.invokeMethod<void>(
+    return FirebasePerformance.channel.invokeMethod<void>(
       '$Trace#incrementMetric',
-      <String, dynamic>{'name': name, 'value': value},
+      <String, dynamic>{'handle': _handle, 'name': name, 'value': value},
     );
   }
 
@@ -93,9 +98,9 @@ class Trace extends PerformanceAttributes {
     if (!_hasStarted || _hasStopped) return Future<void>.value(null);
 
     _metrics[name] = value;
-    return channel.invokeMethod<void>(
+    return FirebasePerformance.channel.invokeMethod<void>(
       '$Trace#setMetric',
-      <String, dynamic>{'name': name, 'value': value},
+      <String, dynamic>{'handle': _handle, 'name': name, 'value': value},
     );
   }
 
@@ -106,9 +111,9 @@ class Trace extends PerformanceAttributes {
   Future<int> getMetric(String name) {
     if (_hasStopped) return Future<int>.value(_metrics[name] ?? 0);
 
-    return channel.invokeMethod<int>(
+    return FirebasePerformance.channel.invokeMethod<int>(
       '$Trace#getMetric',
-      <String, dynamic>{'name': name},
+      <String, dynamic>{'handle': _handle, 'name': name},
     );
   }
 }

From f9f05b7dc276bc07bf88af69190479145e68f2f1 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 29 Apr 2019 23:01:53 -0700
Subject: [PATCH 21/40] Fix some method calls

---
 .../FlutterFirebasePerformance.java                    | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
index 312363fd46e7..ce04044a1ea8 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterFirebasePerformance.java
@@ -73,9 +73,11 @@ private void isPerformanceCollectionEnabled(MethodChannel.Result result) {
     result.success(performance.isPerformanceCollectionEnabled());
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void setPerformanceCollectionEnabled(MethodCall call, MethodChannel.Result result) {
-    final boolean enabled = (Boolean) call.arguments;
-    performance.setPerformanceCollectionEnabled(enabled);
+    final Boolean enable = call.argument("enable");
+    performance.setPerformanceCollectionEnabled(enable);
+
     result.success(null);
   }
 
@@ -84,7 +86,7 @@ private void newTrace(MethodCall call, MethodChannel.Result result) {
     final String name = call.argument("name");
     final Trace trace = performance.newTrace(name);
 
-    final Integer handle = call.argument("handle");
+    final Integer handle = call.argument("traceHandle");
     FirebasePerformancePlugin.addHandler(handle, new FlutterTrace(trace));
 
     result.success(null);
@@ -97,7 +99,7 @@ private void newHttpMetric(MethodCall call, MethodChannel.Result result) {
 
     final HttpMetric metric = performance.newHttpMetric(url, parseHttpMethod(httpMethod));
 
-    final Integer handle = call.argument("handle");
+    final Integer handle = call.argument("httpMetricHandle");
     FirebasePerformancePlugin.addHandler(handle, new FlutterHttpMetric(metric));
 
     result.success(null);

From 1a35bde6491705e7c6590c3cb4e834ee3722b09d Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Mon, 29 Apr 2019 23:38:48 -0700
Subject: [PATCH 22/40] Move ConstantConditions and generic handler call

---
 .../FirebasePerformancePlugin.java            | 31 +++++++------------
 .../FlutterHttpMetric.java                    |  7 ++++-
 .../firebaseperformance/FlutterTrace.java     |  7 ++++-
 3 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
index 11748c4162bc..99a1d82d06e1 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FirebasePerformancePlugin.java
@@ -22,26 +22,16 @@ public static void registerWith(Registrar registrar) {
 
   @Override
   public void onMethodCall(MethodCall call, MethodChannel.Result result) {
-    switch (call.method) {
-      case "FirebasePerformance#instance":
-        FlutterFirebasePerformance.getInstance(call, result);
-        break;
-      case "FirebasePerformance#isPerformanceCollectionEnabled":
-      case "FirebasePerformance#setPerformanceCollectionEnabled":
-      case "FirebasePerformance#newTrace":
-      case "FirebasePerformance#newHttpMetric":
-      case "Trace#start":
-      case "Trace#stop":
-      case "Trace#setMetric":
-      case "Trace#incrementMetric":
-      case "Trace#getMetric":
-      case "PerformanceAttributes#putAttribute":
-      case "PerformanceAttributes#removeAttribute":
-      case "PerformanceAttributes#getAttributes":
-        getHandler(call).onMethodCall(call, result);
-        break;
-      default:
+    if (call.method.equals("FirebasePerformance#instance")) {
+      FlutterFirebasePerformance.getInstance(call, result);
+    } else {
+      final MethodChannel.MethodCallHandler handler = getHandler(call);
+
+      if (handler != null) {
+        handler.onMethodCall(call, result);
+      } else {
         result.notImplemented();
+      }
     }
   }
 
@@ -58,9 +48,10 @@ static void removeHandler(final int handle) {
     handlers.remove(handle);
   }
 
-  @SuppressWarnings("ConstantConditions")
   private static MethodChannel.MethodCallHandler getHandler(final MethodCall call) {
     final Integer handle = call.argument("handle");
+
+    if (handle == null) return null;
     return handlers.get(handle);
   }
 }
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index 0fdc99998af4..a6ff761b0df4 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -8,7 +8,6 @@
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 
-@SuppressWarnings("ConstantConditions")
 public class FlutterHttpMetric implements MethodChannel.MethodCallHandler {
   private final HttpMetric httpMetric;
 
@@ -56,6 +55,7 @@ private void start(MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void stop(MethodCall call, MethodChannel.Result result) {
     httpMetric.stop();
 
@@ -65,12 +65,14 @@ private void stop(MethodCall call, MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void setHttpResponseCode(MethodCall call, MethodChannel.Result result) {
     final Integer httpResponseCode = call.argument("httpResponseCode");
     httpMetric.setHttpResponseCode(httpResponseCode);
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void setRequestPayloadSize(MethodCall call, MethodChannel.Result result) {
     final Number payloadSize = call.argument("requestPayloadSize");
     httpMetric.setRequestPayloadSize(payloadSize.longValue());
@@ -83,12 +85,14 @@ private void setResponseContentType(MethodCall call, MethodChannel.Result result
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void setResponsePayloadSize(MethodCall call, MethodChannel.Result result) {
     final Number payloadSize = call.argument("responsePayloadSize");
     httpMetric.setResponsePayloadSize(payloadSize.longValue());
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void putAttribute(MethodCall call, MethodChannel.Result result) {
     final String attribute = call.argument("attribute");
     final String value = call.argument("value");
@@ -98,6 +102,7 @@ private void putAttribute(MethodCall call, MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void removeAttribute(MethodCall call, MethodChannel.Result result) {
     final String attribute = call.argument("attribute");
     httpMetric.removeAttribute(attribute);
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index 63a469cdcd2f..b9e2fa3fbc6b 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -8,7 +8,6 @@
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 
-@SuppressWarnings("ConstantConditions")
 public class FlutterTrace implements MethodChannel.MethodCallHandler {
   private final Trace trace;
 
@@ -53,6 +52,7 @@ private void start(MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void stop(MethodCall call, MethodChannel.Result result) {
     trace.stop();
 
@@ -62,6 +62,7 @@ private void stop(MethodCall call, MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void setMetric(MethodCall call, MethodChannel.Result result) {
     final String name = call.argument("name");
     final Number value = call.argument("value");
@@ -70,6 +71,7 @@ private void setMetric(MethodCall call, MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void incrementMetric(MethodCall call, MethodChannel.Result result) {
     final String name = call.argument("name");
     final Number value = call.argument("value");
@@ -78,12 +80,14 @@ private void incrementMetric(MethodCall call, MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void getMetric(MethodCall call, MethodChannel.Result result) {
     final String name = call.argument("name");
 
     result.success(trace.getLongMetric(name));
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void putAttribute(MethodCall call, MethodChannel.Result result) {
     final String attribute = call.argument("attribute");
     final String value = call.argument("value");
@@ -93,6 +97,7 @@ private void putAttribute(MethodCall call, MethodChannel.Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("ConstantConditions")
   private void removeAttribute(MethodCall call, MethodChannel.Result result) {
     final String attribute = call.argument("attribute");
     trace.removeAttribute(attribute);

From 3e6fe50bc5d2c72019479ab05c1e3c1b36b5dd28 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 12:18:27 -0700
Subject: [PATCH 23/40] Redesign for iOS

---
 .../ios/Classes/FLTFirebasePerformance.m      | 51 ++++++-------------
 .../ios/Classes/FLTHttpMetric.m               | 17 +++----
 .../ios/Classes/FLTTrace.m                    | 17 +++----
 .../ios/Classes/FirebasePerformancePlugin.h   | 12 ++---
 .../ios/Classes/FirebasePerformancePlugin.m   | 51 +++++++++++++++++--
 5 files changed, 81 insertions(+), 67 deletions(-)

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
index 62879def378f..eff5e62672d1 100644
--- a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -5,31 +5,21 @@
 #import "FirebasePerformancePlugin.h"
 
 @interface FLTFirebasePerformance ()
-@property id<FlutterPluginRegistrar> registrar;
 @property FIRPerformance *performance;
 @end
 
 @implementation FLTFirebasePerformance
 + (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
 
-- (instancetype _Nonnull)initWithRegistrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar {
-  self = [self init];
-  if (self) {
-    _performance = [FIRPerformance sharedInstance];
-    _registrar = registrar;
-  }
-
-  return self;
++ (void)sharedInstanceWithCall:(FlutterMethodCall*)call result:(FlutterResult)result {
+  NSNumber *handle = call.arguments[@"handle"];
+  [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:[FLTFirebasePerformance new]];
 }
 
 - (instancetype)init {
   self = [super init];
   if (self) {
-    if (![FIRApp appNamed:@"__FIRAPP_DEFAULT"]) {
-      NSLog(@"Configuring the default Firebase app...");
-      [FIRApp configure];
-      NSLog(@"Configured the default Firebase app %@.", [FIRApp defaultApp].name);
-    }
+    _performance = [FIRPerformance sharedInstance];
   }
 
   return self;
@@ -54,43 +44,32 @@ - (void)isPerformanceCollectionEnabled:(FlutterResult)result {
 }
 
 - (void)setPerformanceCollectionEnabled:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSNumber *enable = call.arguments;
+  NSNumber *enable = call.arguments[@"enable"];
   [_performance setDataCollectionEnabled:[enable boolValue]];
   result(nil);
 }
 
 - (void)newTrace:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSString *traceName = call.arguments[@"traceName"];
-  FIRTrace *trace = [_performance traceWithName:traceName];
+  NSString *name = call.arguments[@"name"];
+  FIRTrace *trace = [_performance traceWithName:name];
+  FLTTrace *handler = [[FLTTrace alloc] initWithTrace:trace];
 
-  NSString *channelName = call.arguments[@"channelName"];
-  FlutterMethodChannel* channel = [FlutterMethodChannel
-                                   methodChannelWithName:channelName
-                                   binaryMessenger:[_registrar messenger]];
+  NSNumber *handle = call.arguments[@"traceHandle"];
+  [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:handler];
 
-  FLTTrace *delegate = [[FLTTrace alloc] initWithTrace:trace registrar:_registrar channel:channel];
-  [_registrar addMethodCallDelegate:delegate channel:channel];
   result(nil);
 }
 
 - (void)newHttpMetric:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSString *httpMethod = call.arguments[@"httpMethod"];
-  FIRHTTPMethod method = [FLTFirebasePerformance parseHttpMethod:httpMethod];
-
-  NSString *urlString = call.arguments[@"url"];
-  NSURL *url = [NSURL URLWithString:urlString];
+  FIRHTTPMethod method = [FLTFirebasePerformance parseHttpMethod:call.arguments[@"httpMethod"]];
+  NSURL *url = [NSURL URLWithString:call.arguments[@"url"]];
 
   FIRHTTPMetric *metric = [[FIRHTTPMetric alloc] initWithURL:url HTTPMethod:method];
+  FLTHttpMetric *handler = [[FLTHttpMetric alloc] initWithHTTPMetric:metric];
 
-  NSString *channelName = call.arguments[@"channelName"];
-  FlutterMethodChannel *channel = [FlutterMethodChannel
-                                   methodChannelWithName:channelName
-                                   binaryMessenger:[_registrar messenger]];
+  NSNumber *handle = call.arguments[@"httpMetricHandle"];
+  [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:handler];
 
-  FLTHttpMetric *delegate = [[FLTHttpMetric alloc] initWithHTTPMetric:metric
-                                                            registrar:_registrar
-                                                              channel:channel];
-  [_registrar addMethodCallDelegate:delegate channel:channel];
   result(nil);
 }
 
diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
index 5d6ca4df6552..376c03d7515a 100644
--- a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -6,21 +6,15 @@
 
 @interface FLTHttpMetric ()
 @property FIRHTTPMetric *metric;
-@property id<FlutterPluginRegistrar> registrar;
-@property FlutterMethodChannel *channel;
 @end
 
 @implementation FLTHttpMetric
 + (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
 
-- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *)metric
-                                  registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
-                                    channel:(FlutterMethodChannel *)channel {
+- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *)metric {
   self = [self init];
   if (self) {
     _metric = metric;
-    _registrar = registrar;
-    _channel = channel;
   }
 
   return self;
@@ -30,7 +24,7 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
   if ([@"HttpMetric#start" isEqualToString:call.method]) {
     [self start:result];
   } else if ([@"HttpMetric#stop" isEqualToString:call.method]) {
-    [self stop:result];
+    [self stop:call result:result];
   } else if ([@"HttpMetric#httpResponseCode" isEqualToString:call.method]) {
     [self setHttpResponseCode:call result:result];
   } else if ([@"HttpMetric#requestPayloadSize" isEqualToString:call.method]) {
@@ -55,9 +49,12 @@ - (void)start:(FlutterResult)result {
   result(nil);
 }
 
-- (void)stop:(FlutterResult)result {
+- (void)stop:(FlutterMethodCall *)call result:(FlutterResult)result {
   [_metric stop];
-  [_registrar addMethodCallDelegate:nil channel:nil];
+
+  NSNumber *handle = call.arguments[@"handle"];
+  [FLTFirebasePerformancePlugin removeMethodHandler:handle];
+
   result(nil);
 }
 
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
index 72e94a17638c..9cbd9d274234 100644
--- a/packages/firebase_performance/ios/Classes/FLTTrace.m
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -6,20 +6,14 @@
 
 @interface FLTTrace ()
 @property FIRTrace *trace;
-@property id<FlutterPluginRegistrar> registrar;
-@property FlutterMethodChannel *channel;
 @end
 
 @implementation FLTTrace
 + (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
 
-- (instancetype _Nonnull)initWithTrace:(FIRTrace *)trace
-                             registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
-                               channel:(FlutterMethodChannel *)channel {
+- (instancetype _Nonnull)initWithTrace:(FIRTrace *)trace {
   self = [self init];
   if (self) {
-    _registrar = registrar;
-    _channel = channel;
     _trace = trace;
   }
 
@@ -30,7 +24,7 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
   if ([@"Trace#start" isEqualToString:call.method]) {
     [self start:result];
   } else if ([@"Trace#stop" isEqualToString:call.method]) {
-    [self stop:result];
+    [self stop:call result:result];
   } else if ([@"Trace#setMetric" isEqualToString:call.method]) {
     [self setMetric:call result:result];
   } else if ([@"Trace#incrementMetric" isEqualToString:call.method]) {
@@ -53,9 +47,12 @@ - (void)start:(FlutterResult)result {
   result(nil);
 }
 
-- (void)stop:(FlutterResult)result {
+- (void)stop:(FlutterMethodCall *)call result:(FlutterResult)result {
   [_trace stop];
-  [_registrar addMethodCallDelegate:nil channel:_channel];
+
+  NSNumber *handle = call.arguments[@"handle"];
+  [FLTFirebasePerformancePlugin removeMethodHandler:handle];
+
   result(nil);
 }
 
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index 8eda01fb8dad..cc5de2523517 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -2,20 +2,18 @@
 #import <Flutter/Flutter.h>
 
 @interface FLTFirebasePerformancePlugin : NSObject <FlutterPlugin>
++ (void)addMethodHandler:(NSNumber *_Nonnull)handle methodHandler:(id<FlutterPlugin>_Nonnull)handler;
++ (void)removeMethodHandler:(NSNumber *_Nonnull)handle;
 @end
 
 @interface FLTFirebasePerformance : NSObject<FlutterPlugin>
-- (instancetype _Nonnull)initWithRegistrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar;
++ (void)sharedInstanceWithCall:(FlutterMethodCall *_Nonnull)call result:(FlutterResult _Nonnull)result;
 @end
 
 @interface FLTTrace : NSObject<FlutterPlugin>
-- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace
-                             registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
-                               channel:(FlutterMethodChannel *_Nonnull)channel;
+- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
 @end
 
 @interface FLTHttpMetric : NSObject<FlutterPlugin>
-- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric
-                                  registrar:(NSObject<FlutterPluginRegistrar> *_Nonnull)registrar
-                                    channel:(FlutterMethodChannel *_Nonnull)channel;
+- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric;
 @end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index e96ef47e288a..80703623a1fc 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -5,14 +5,57 @@
 #import "FirebasePerformancePlugin.h"
 
 @implementation FLTFirebasePerformancePlugin
+static NSMutableDictionary<NSNumber *, id<FlutterPlugin>> *methodHandlers;
+
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
+  methodHandlers = [NSMutableDictionary new];
+
   FlutterMethodChannel *channel =
-      [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/firebase_performance"
-                                  binaryMessenger:[registrar messenger]];
+  [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/firebase_performance"
+                              binaryMessenger:[registrar messenger]];
 
-  FLTFirebasePerformance *instance = [[FLTFirebasePerformance alloc] initWithRegistrar:registrar];
+  FLTFirebasePerformancePlugin *instance = [FLTFirebasePerformancePlugin new];
   [registrar addMethodCallDelegate:instance channel:channel];
 }
 
-- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {}
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    if (![FIRApp appNamed:@"__FIRAPP_DEFAULT"]) {
+      NSLog(@"Configuring the default Firebase app...");
+      [FIRApp configure];
+      NSLog(@"Configured the default Firebase app %@.", [FIRApp defaultApp].name);
+    }
+  }
+
+  return self;
+}
+
+- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
+  if ([@"FirebasePerformance#instance" isEqualToString:call.method]) {
+    [FLTFirebasePerformance sharedInstanceWithCall:call result:result];
+    result(nil);
+  } else {
+    NSNumber *handle = call.arguments[@"handle"];
+
+    if (![handle isEqual:[NSNull null]]) {
+      [methodHandlers[handle] handleMethodCall:call result:result];
+    } else {
+      result(FlutterMethodNotImplemented);
+    }
+  }
+}
+
++ (void)addMethodHandler:(NSNumber *)handle methodHandler:(id<FlutterPlugin>)handler {
+  if (methodHandlers[handle]) {
+    NSString *reason = [[NSString alloc] initWithFormat:@"Object for handle already exists: %d", handle.intValue];
+    @throw [[NSException alloc] initWithName:NSInvalidArgumentException reason:reason userInfo:nil];
+  }
+
+  methodHandlers[handle] = handler;
+}
+
++ (void)removeMethodHandler:(NSNumber *)handle {
+  [methodHandlers removeObjectForKey:handle];
+}
 @end

From 21fd8cbdb6a2b043a6a08ab4c6ad510962216fa8 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 12:28:07 -0700
Subject: [PATCH 24/40] Formatting

---
 .../ios/Classes/FLTFirebasePerformance.m             |  5 +++--
 .../firebase_performance/ios/Classes/FLTHttpMetric.m |  3 ++-
 packages/firebase_performance/ios/Classes/FLTTrace.m |  3 ++-
 .../ios/Classes/FirebasePerformancePlugin.h          | 12 +++++++-----
 .../ios/Classes/FirebasePerformancePlugin.m          |  7 ++++---
 5 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
index eff5e62672d1..7737df7d67a6 100644
--- a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -9,9 +9,10 @@ @interface FLTFirebasePerformance ()
 @end
 
 @implementation FLTFirebasePerformance
-+ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
++ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
+}
 
-+ (void)sharedInstanceWithCall:(FlutterMethodCall*)call result:(FlutterResult)result {
++ (void)sharedInstanceWithCall:(FlutterMethodCall *)call result:(FlutterResult)result {
   NSNumber *handle = call.arguments[@"handle"];
   [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:[FLTFirebasePerformance new]];
 }
diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
index 376c03d7515a..8c0bc1f86b35 100644
--- a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -9,7 +9,8 @@ @interface FLTHttpMetric ()
 @end
 
 @implementation FLTHttpMetric
-+ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
++ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
+}
 
 - (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *)metric {
   self = [self init];
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
index 9cbd9d274234..510e8f5fc135 100644
--- a/packages/firebase_performance/ios/Classes/FLTTrace.m
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -9,7 +9,8 @@ @interface FLTTrace ()
 @end
 
 @implementation FLTTrace
-+ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {}
++ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
+}
 
 - (instancetype _Nonnull)initWithTrace:(FIRTrace *)trace {
   self = [self init];
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index cc5de2523517..f50df538a254 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -2,18 +2,20 @@
 #import <Flutter/Flutter.h>
 
 @interface FLTFirebasePerformancePlugin : NSObject <FlutterPlugin>
-+ (void)addMethodHandler:(NSNumber *_Nonnull)handle methodHandler:(id<FlutterPlugin>_Nonnull)handler;
++ (void)addMethodHandler:(NSNumber *_Nonnull)handle
+           methodHandler:(id<FlutterPlugin>_Nonnull)handler;
 + (void)removeMethodHandler:(NSNumber *_Nonnull)handle;
 @end
 
-@interface FLTFirebasePerformance : NSObject<FlutterPlugin>
-+ (void)sharedInstanceWithCall:(FlutterMethodCall *_Nonnull)call result:(FlutterResult _Nonnull)result;
+@interface FLTFirebasePerformance : NSObject <FlutterPlugin>
++ (void)sharedInstanceWithCall:(FlutterMethodCall *_Nonnull)call
+                        result:(FlutterResult _Nonnull)result;
 @end
 
-@interface FLTTrace : NSObject<FlutterPlugin>
+@interface FLTTrace : NSObject <FlutterPlugin>
 - (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
 @end
 
-@interface FLTHttpMetric : NSObject<FlutterPlugin>
+@interface FLTHttpMetric : NSObject <FlutterPlugin>
 - (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric;
 @end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index 80703623a1fc..82298f0ae970 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -11,8 +11,8 @@ + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   methodHandlers = [NSMutableDictionary new];
 
   FlutterMethodChannel *channel =
-  [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/firebase_performance"
-                              binaryMessenger:[registrar messenger]];
+      [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/firebase_performance"
+                                  binaryMessenger:[registrar messenger]];
 
   FLTFirebasePerformancePlugin *instance = [FLTFirebasePerformancePlugin new];
   [registrar addMethodCallDelegate:instance channel:channel];
@@ -48,7 +48,8 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
 
 + (void)addMethodHandler:(NSNumber *)handle methodHandler:(id<FlutterPlugin>)handler {
   if (methodHandlers[handle]) {
-    NSString *reason = [[NSString alloc] initWithFormat:@"Object for handle already exists: %d", handle.intValue];
+    NSString *reason =
+        [[NSString alloc] initWithFormat:@"Object for handle already exists: %d", handle.intValue];
     @throw [[NSException alloc] initWithName:NSInvalidArgumentException reason:reason userInfo:nil];
   }
 

From 83aa1a9313718d7cef2fa924be6e2597525138f4 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 12:49:20 -0700
Subject: [PATCH 25/40] formattinn

---
 .../ios/Classes/FirebasePerformancePlugin.h                     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index f50df538a254..3c45bd342866 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -3,7 +3,7 @@
 
 @interface FLTFirebasePerformancePlugin : NSObject <FlutterPlugin>
 + (void)addMethodHandler:(NSNumber *_Nonnull)handle
-           methodHandler:(id<FlutterPlugin>_Nonnull)handler;
+           methodHandler:(id<FlutterPlugin> _Nonnull)handler;
 + (void)removeMethodHandler:(NSNumber *_Nonnull)handle;
 @end
 

From acfa84afd71064be5bb8f921448675a3623c1998 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 12:59:44 -0700
Subject: [PATCH 26/40] integeration testing

---
 .../test_driver/firebase_performance.dart     | 46 ++++++++++++++-----
 1 file changed, 35 insertions(+), 11 deletions(-)

diff --git a/packages/firebase_performance/example/test_driver/firebase_performance.dart b/packages/firebase_performance/example/test_driver/firebase_performance.dart
index 295a5da94ad2..98c192bf5ff5 100644
--- a/packages/firebase_performance/example/test_driver/firebase_performance.dart
+++ b/packages/firebase_performance/example/test_driver/firebase_performance.dart
@@ -25,20 +25,44 @@ void main() {
       expect(disabled, isFalse);
     });
 
-    // TODO(bparrishMines): Rewrite integration test when iOS portion is written.
-    /*
-    test('metric', () async {
+    test('trace', () async {
       final Trace trace = performance.newTrace('test');
-      trace.putAttribute('testAttribute', 'foo');
-      trace.attributes['testAttribute2'] = 'bar';
+
       await trace.start();
-      trace.incrementMetric('testMetric', 1);
+
+      trace.putAttribute('testAttribute', 'foo');
+      final Map<String, String> attributes = await trace.getAttributes();
+      expect(attributes, <String, String>{'testAttribute': 'foo'});
+
+      trace.incrementMetric('testMetric', 22);
+      final int metric = await trace.getMetric('testMetric');
+      expect(metric, 22);
+
+      trace.setMetric('testMetric2', 33);
+      final int metric2 = await trace.getMetric('testMetric2');
+      expect(metric2, 33);
+
       await trace.stop();
-      expect(trace.getAttribute('testAttribute'), 'foo');
-      expect(trace.attributes['testAttribute'], 'foo');
-      expect(trace.getAttribute('testAttribute2'), null);
-      expect(trace.getAttribute('testMetric'), null);
     });
-    */
+
+    test('httpmetric', () async {
+      final HttpMetric httpMetric = performance.newHttpMetric(
+        'www.google.com',
+        HttpMethod.Connect,
+      );
+
+      await httpMetric.start();
+
+      httpMetric.putAttribute('testAttribute', 'foo');
+      final Map<String, String> attributes = await httpMetric.getAttributes();
+      expect(attributes, <String, String>{'testAttribute': 'foo'});
+
+      httpMetric.httpResponseCode = 45;
+      httpMetric.requestPayloadSize = 45;
+      httpMetric.responseContentType = 'testString';
+      httpMetric.responsePayloadSize = 45;
+
+      await httpMetric.stop();
+    });
   });
 }

From 9d8ff822d2d5a132d570f08a30c94f21a4b9745e Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 13:56:15 -0700
Subject: [PATCH 27/40] Update testing

---
 .../lib/src/performance_attributes.dart       |  18 +-
 .../firebase_performance/lib/src/trace.dart   |   3 +-
 .../test/firebase_performance_test.dart       | 182 ++++++++++--------
 3 files changed, 115 insertions(+), 88 deletions(-)

diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index c12abb499655..119567a1eaf0 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -22,7 +22,7 @@ abstract class PerformanceAttributes {
 
   int get _handle;
 
-  /// Sets a String [value] for the specified [attribute].
+  /// Sets a String [value] for the specified attribute with [name].
   ///
   /// Updates the value of the attribute if the attribute already exists.
   /// The maximum number of attributes that can be added are
@@ -31,34 +31,34 @@ abstract class PerformanceAttributes {
   /// Name of the attribute has max length of [maxAttributeKeyLength]
   /// characters. Value of the attribute has max length of
   /// [maxAttributeValueLength] characters.
-  Future<void> putAttribute(String attribute, String value) {
+  Future<void> putAttribute(String name, String value) {
     if (!_hasStarted ||
         _hasStopped ||
-        attribute.length > maxAttributeKeyLength ||
+        name.length > maxAttributeKeyLength ||
         value.length > maxAttributeValueLength ||
         _attributes.length == 5) {
       return Future<void>.value(null);
     }
 
-    _attributes[attribute] = value;
+    _attributes[name] = value;
     return FirebasePerformance.channel.invokeMethod<void>(
       '$PerformanceAttributes#putAttribute',
       <String, dynamic>{
         'handle': _handle,
-        'attribute': attribute,
+        'name': name,
         'value': value,
       },
     );
   }
 
-  /// Removes an already added [attribute].
-  Future<void> removeAttribute(String attribute) {
+  /// Removes an already added attribute with [name].
+  Future<void> removeAttribute(String name) {
     if (!_hasStarted || _hasStopped) return Future<void>.value(null);
 
-    _attributes.remove(attribute);
+    _attributes.remove(name);
     return FirebasePerformance.channel.invokeMethod<void>(
       '$PerformanceAttributes#removeAttribute',
-      <String, dynamic>{'handle': _handle, 'attribute': attribute},
+      <String, dynamic>{'handle': _handle, 'name': name},
     );
   }
 
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index 5f8a98ad0151..f77e0f7a3683 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -78,10 +78,11 @@ class Trace extends PerformanceAttributes {
   /// not been started or has already been stopped, returns immediately without
   /// taking action.
   Future<void> incrementMetric(String name, int value) {
-    if (!_hasStarted || _hasStopped || _metrics[name] == null) {
+    if (!_hasStarted || _hasStopped) {
       return Future<void>.value(null);
     }
 
+    _metrics.putIfAbsent(name, () => 0);
     _metrics[name] += value;
     return FirebasePerformance.channel.invokeMethod<void>(
       '$Trace#incrementMetric',
diff --git a/packages/firebase_performance/test/firebase_performance_test.dart b/packages/firebase_performance/test/firebase_performance_test.dart
index 7ce36bb65294..c2dbd1997c0a 100644
--- a/packages/firebase_performance/test/firebase_performance_test.dart
+++ b/packages/firebase_performance/test/firebase_performance_test.dart
@@ -9,10 +9,13 @@ import 'package:flutter_test/flutter_test.dart';
 
 void main() {
   group('$FirebasePerformance', () {
-    final FirebasePerformance performance = FirebasePerformance.instance;
+    FirebasePerformance performance;
     final List<MethodCall> log = <MethodCall>[];
     bool isPerformanceCollectionEnabledResult;
 
+    int firebasePerformanceHandle;
+    int nextHandle = 0;
+
     setUp(() {
       FirebasePerformance.channel
           .setMockMethodCallHandler((MethodCall methodCall) async {
@@ -27,6 +30,19 @@ void main() {
       log.clear();
     });
 
+    test('instance', () {
+      firebasePerformanceHandle = nextHandle++;
+
+      performance = FirebasePerformance.instance;
+
+      expect(log, <Matcher>[
+        isMethodCall(
+          'FirebasePerformance#instance',
+          arguments: <String, dynamic>{'handle': firebasePerformanceHandle},
+        ),
+      ]);
+    });
+
     test('isPerformanceCollectionEnabled', () async {
       isPerformanceCollectionEnabledResult = true;
       final bool enabled = await performance.isPerformanceCollectionEnabled();
@@ -39,11 +55,11 @@ void main() {
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#isPerformanceCollectionEnabled',
-          arguments: null,
+          arguments: <String, dynamic>{'handle': firebasePerformanceHandle},
         ),
         isMethodCall(
           'FirebasePerformance#isPerformanceCollectionEnabled',
-          arguments: null,
+          arguments: <String, dynamic>{'handle': firebasePerformanceHandle},
         ),
       ]);
     });
@@ -55,24 +71,31 @@ void main() {
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#setPerformanceCollectionEnabled',
-          arguments: true,
+          arguments: <String, dynamic>{
+            'handle': firebasePerformanceHandle,
+            'enable': true,
+          },
         ),
         isMethodCall(
           'FirebasePerformance#setPerformanceCollectionEnabled',
-          arguments: false,
+          arguments: <String, dynamic>{
+            'handle': firebasePerformanceHandle,
+            'enable': false,
+          },
         ),
       ]);
     });
 
     test('newTrace', () {
-      final Trace trace = performance.newTrace('test-trace');
+      performance.newTrace('test-trace');
 
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#newTrace',
           arguments: <String, dynamic>{
-            'channelName': trace.channel.name,
-            'traceName': 'test-trace',
+            'handle': firebasePerformanceHandle,
+            'traceHandle': nextHandle++,
+            'name': 'test-trace',
           },
         ),
       ]);
@@ -80,17 +103,14 @@ void main() {
 
     test('newHttpMetric', () {
       final String url = 'https://google.com';
-
-      final HttpMetric metric = performance.newHttpMetric(
-        url,
-        HttpMethod.Connect,
-      );
+      performance.newHttpMetric(url, HttpMethod.Connect);
 
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#newHttpMetric',
           arguments: <String, dynamic>{
-            'channelName': metric.channel.name,
+            'handle': firebasePerformanceHandle,
+            'httpMetricHandle': nextHandle++,
             'url': url,
             'httpMethod': HttpMethod.Connect.toString(),
           },
@@ -102,16 +122,14 @@ void main() {
       final String url = 'https://google.com';
       final HttpMethod method = HttpMethod.Connect;
 
-      final HttpMetric metric = performance.newHttpMetric(
-        'https://google.com',
-        method,
-      );
+      performance.newHttpMetric('https://google.com', method);
 
       expect(log, <Matcher>[
         isMethodCall(
           'FirebasePerformance#newHttpMetric',
           arguments: <String, dynamic>{
-            'channelName': metric.channel.name,
+            'handle': firebasePerformanceHandle,
+            'httpMetricHandle': nextHandle++,
             'url': url,
             'httpMethod': method.toString(),
           },
@@ -121,54 +139,55 @@ void main() {
 
     group('$Trace', () {
       Trace testTrace;
-      final List<MethodCall> traceLog = <MethodCall>[];
+      int currentTestTraceHandle;
 
       setUp(() {
         testTrace = performance.newTrace('test');
-        testTrace.channel
-            .setMockMethodCallHandler((MethodCall methodCall) async {
-          traceLog.add(methodCall);
-          switch (methodCall.method) {
-            case 'FirebasePerformance#isPerformanceCollectionEnabled':
-              return true;
-            default:
-              return null;
-          }
-        });
-        traceLog.clear();
+        currentTestTraceHandle = nextHandle++;
+        log.clear();
       });
 
       test('start', () {
         testTrace.start();
 
-        expect(traceLog, <Matcher>[
-          isMethodCall('Trace#start', arguments: null),
+        expect(log, <Matcher>[
+          isMethodCall(
+            'Trace#start',
+            arguments: <String, dynamic>{'handle': currentTestTraceHandle},
+          ),
         ]);
       });
 
       test('stop', () {
+        testTrace.start();
+        log.clear();
+
         testTrace.stop();
 
-        expect(traceLog, <Matcher>[
-          isMethodCall('Trace#stop', arguments: null),
+        expect(log, <Matcher>[
+          isMethodCall(
+            'Trace#stop',
+            arguments: <String, dynamic>{'handle': currentTestTraceHandle},
+          ),
         ]);
       });
 
       test('incrementMetric', () {
-        final String name = 'counter1';
-        final int value = 45;
-        final int increment = 3;
-
         testTrace.start();
-        testTrace.setMetric(name, value);
-        traceLog.clear();
+        log.clear();
 
+        final String name = 'metric1';
+        final int increment = 3;
         testTrace.incrementMetric(name, increment);
 
-        expect(traceLog, <Matcher>[
+        expect(log, <Matcher>[
           isMethodCall(
             'Trace#incrementMetric',
-            arguments: <String, dynamic>{'name': name, 'value': increment},
+            arguments: <String, dynamic>{
+              'handle': currentTestTraceHandle,
+              'name': name,
+              'value': increment,
+            },
           ),
         ]);
       });
@@ -176,78 +195,82 @@ void main() {
 
     group('$HttpMetric', () {
       HttpMetric testMetric;
-      final List<MethodCall> httpMetricLog = <MethodCall>[];
+      int currentTestMetricHandle;
 
       setUp(() {
         testMetric = performance.newHttpMetric(
           'https://google.com',
           HttpMethod.Get,
         );
-        testMetric.channel
-            .setMockMethodCallHandler((MethodCall methodCall) async {
-          httpMetricLog.add(methodCall);
-          switch (methodCall.method) {
-            case 'FirebasePerformance#isPerformanceCollectionEnabled':
-              return true;
-            default:
-              return null;
-          }
-        });
-        httpMetricLog.clear();
+        currentTestMetricHandle = nextHandle++;
+        log.clear();
       });
 
       test('start', () {
         testMetric.start();
 
-        expect(httpMetricLog, <Matcher>[
-          isMethodCall('HttpMetric#start', arguments: null),
+        expect(log, <Matcher>[
+          isMethodCall(
+            'HttpMetric#start',
+            arguments: <String, dynamic>{'handle': currentTestMetricHandle},
+          ),
         ]);
       });
 
       test('stop', () {
+        testMetric.start();
+        log.clear();
+
         testMetric.stop();
 
-        expect(httpMetricLog, <Matcher>[
-          isMethodCall('HttpMetric#stop', arguments: null),
+        expect(log, <Matcher>[
+          isMethodCall(
+            'HttpMetric#stop',
+            arguments: <String, dynamic>{'handle': currentTestMetricHandle},
+          ),
         ]);
       });
     });
 
     group('$PerformanceAttributes', () {
       Trace attributeTrace;
-      final List<MethodCall> attributeLog = <MethodCall>[];
+      int currentTraceHandle;
+
       final Map<dynamic, dynamic> getAttributesResult = <dynamic, dynamic>{
         'a1': 'hello',
         'a2': 'friend',
       };
 
       setUp(() {
-        attributeTrace = performance.newTrace('trace');
-        attributeTrace.channel
+        FirebasePerformance.channel
             .setMockMethodCallHandler((MethodCall methodCall) async {
-          attributeLog.add(methodCall);
-          if (methodCall.method == 'PerformanceAttributes#getAttributes') {
-            return getAttributesResult;
+          log.add(methodCall);
+          switch (methodCall.method) {
+            case 'PerformanceAttributes#getAttributes':
+              return getAttributesResult;
+            default:
+              return null;
           }
-
-          return null;
         });
 
+        attributeTrace = performance.newTrace('trace');
+        currentTraceHandle = nextHandle++;
         attributeTrace.start();
-        attributeLog.clear();
+        log.clear();
       });
 
       test('putAttribute', () {
-        final String attribute = 'attr1';
+        final String name = 'attr1';
         final String value = 'apple';
 
-        attributeTrace.putAttribute(attribute, value);
+        attributeTrace.putAttribute(name, value);
 
-        expect(attributeLog, <Matcher>[
+        expect(log, <Matcher>[
           isMethodCall(
             'PerformanceAttributes#putAttribute',
             arguments: <String, dynamic>{
-              'attribute': attribute,
+              'handle': currentTraceHandle,
+              'name': name,
               'value': value,
             },
           ),
@@ -255,13 +278,16 @@ void main() {
       });
 
       test('removeAttribute', () {
-        final String attribute = 'attr1';
-        attributeTrace.removeAttribute(attribute);
+        final String name = 'attr1';
+        attributeTrace.removeAttribute(name);
 
-        expect(attributeLog, <Matcher>[
+        expect(log, <Matcher>[
           isMethodCall(
             'PerformanceAttributes#removeAttribute',
-            arguments: attribute,
+            arguments: <String, dynamic>{
+              'handle': currentTraceHandle,
+              'name': name,
+            },
           ),
         ]);
       });
@@ -269,10 +295,10 @@ void main() {
       test('getAttributes', () async {
         final Map<String, String> result = await attributeTrace.getAttributes();
 
-        expect(attributeLog, <Matcher>[
+        expect(log, <Matcher>[
           isMethodCall(
             'PerformanceAttributes#getAttributes',
-            arguments: null,
+            arguments: <String, dynamic>{'handle': currentTraceHandle},
           ),
         ]);
 

From 2a3f0b2b45f82712dc70c4d0663366cf9753c804 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 13:57:53 -0700
Subject: [PATCH 28/40] attribute to name

---
 .../plugins/firebaseperformance/FlutterHttpMetric.java    | 8 ++++----
 .../flutter/plugins/firebaseperformance/FlutterTrace.java | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
index a6ff761b0df4..2e2f2e6e4ed3 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterHttpMetric.java
@@ -94,18 +94,18 @@ private void setResponsePayloadSize(MethodCall call, MethodChannel.Result result
 
   @SuppressWarnings("ConstantConditions")
   private void putAttribute(MethodCall call, MethodChannel.Result result) {
-    final String attribute = call.argument("attribute");
+    final String name = call.argument("name");
     final String value = call.argument("value");
 
-    httpMetric.putAttribute(attribute, value);
+    httpMetric.putAttribute(name, value);
 
     result.success(null);
   }
 
   @SuppressWarnings("ConstantConditions")
   private void removeAttribute(MethodCall call, MethodChannel.Result result) {
-    final String attribute = call.argument("attribute");
-    httpMetric.removeAttribute(attribute);
+    final String name = call.argument("name");
+    httpMetric.removeAttribute(name);
 
     result.success(null);
   }
diff --git a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
index b9e2fa3fbc6b..0bcb54f34834 100644
--- a/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
+++ b/packages/firebase_performance/android/src/main/java/io/flutter/plugins/firebaseperformance/FlutterTrace.java
@@ -89,18 +89,18 @@ private void getMetric(MethodCall call, MethodChannel.Result result) {
 
   @SuppressWarnings("ConstantConditions")
   private void putAttribute(MethodCall call, MethodChannel.Result result) {
-    final String attribute = call.argument("attribute");
+    final String name = call.argument("name");
     final String value = call.argument("value");
 
-    trace.putAttribute(attribute, value);
+    trace.putAttribute(name, value);
 
     result.success(null);
   }
 
   @SuppressWarnings("ConstantConditions")
   private void removeAttribute(MethodCall call, MethodChannel.Result result) {
-    final String attribute = call.argument("attribute");
-    trace.removeAttribute(attribute);
+    final String name = call.argument("name");
+    trace.removeAttribute(name);
 
     result.success(null);
   }

From 96ffe4981bee8c162ebbec472c6ea94b0f6d1940 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 15:00:33 -0700
Subject: [PATCH 29/40] Fix method call name

---
 packages/firebase_performance/ios/Classes/FLTHttpMetric.m | 6 +++---
 packages/firebase_performance/ios/Classes/FLTTrace.m      | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
index 8c0bc1f86b35..af92b59d224d 100644
--- a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -34,11 +34,11 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     [self responseContentType:call result:result];
   } else if ([@"HttpMetric#responsePayloadSize" isEqualToString:call.method]) {
     [self responsePayloadSize:call result:result];
-  } else if ([@"HttpMetric#putAttribute" isEqualToString:call.method]) {
+  } else if ([@"PerformanceAttributes#putAttribute" isEqualToString:call.method]) {
     [self putAttribute:call result:result];
-  } else if ([@"HttpMetric#removeAttribute" isEqualToString:call.method]) {
+  } else if ([@"PerformanceAttributes#removeAttribute" isEqualToString:call.method]) {
     [self removeAttribute:call result:result];
-  } else if ([@"HttpMetric#getAttributes" isEqualToString:call.method]) {
+  } else if ([@"PerformanceAttributes#getAttributes" isEqualToString:call.method]) {
     [self getAttributes:result];
   } else {
     result(FlutterMethodNotImplemented);
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
index 510e8f5fc135..9336268ba68d 100644
--- a/packages/firebase_performance/ios/Classes/FLTTrace.m
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -32,11 +32,11 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     [self incrementMetric:call result:result];
   } else if ([@"Trace#getMetric" isEqualToString:call.method]) {
     [self getMetric:call result:result];
-  } else if ([@"Trace#putAttribute" isEqualToString:call.method]) {
+  } else if ([@"PerformanceAttributes#putAttribute" isEqualToString:call.method]) {
     [self putAttribute:call result:result];
-  } else if ([@"Trace#removeAttribute" isEqualToString:call.method]) {
+  } else if ([@"PerformanceAttributes#removeAttribute" isEqualToString:call.method]) {
     [self removeAttribute:call result:result];
-  } else if ([@"Trace#getAttributes" isEqualToString:call.method]) {
+  } else if ([@"PerformanceAttributes#getAttributes" isEqualToString:call.method]) {
     [self getAttributes:result];
   } else {
     result(FlutterMethodNotImplemented);

From ecd0addcad64f0367017bfa8b3c75da6dbe6e876 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 15:59:29 -0700
Subject: [PATCH 30/40] use block notation

---
 packages/firebase_performance/ios/Classes/FLTHttpMetric.m | 2 +-
 packages/firebase_performance/ios/Classes/FLTTrace.m      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
index af92b59d224d..64a622aeb2d7 100644
--- a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -109,6 +109,6 @@ - (void)removeAttribute:(FlutterMethodCall *)call result:(FlutterResult)result {
 }
 
 - (void)getAttributes:(FlutterResult)result {
-  result(_metric.attributes);
+  result([_metric attributes]);
 }
 @end
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
index 9336268ba68d..a522e3d38a39 100644
--- a/packages/firebase_performance/ios/Classes/FLTTrace.m
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -96,6 +96,6 @@ - (void)removeAttribute:(FlutterMethodCall *)call result:(FlutterResult)result {
 }
 
 - (void)getAttributes:(FlutterResult)result {
-  result(_trace.attributes);
+  result([_trace attributes]);
 }
 @end

From f1b7a7e5c597e9377dbfa5362f22f9e4a0fb5bf8 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 16:51:26 -0700
Subject: [PATCH 31/40] Missed https://

---
 .../example/test_driver/firebase_performance.dart               | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/firebase_performance/example/test_driver/firebase_performance.dart b/packages/firebase_performance/example/test_driver/firebase_performance.dart
index 98c192bf5ff5..ae6d62069690 100644
--- a/packages/firebase_performance/example/test_driver/firebase_performance.dart
+++ b/packages/firebase_performance/example/test_driver/firebase_performance.dart
@@ -47,7 +47,7 @@ void main() {
 
     test('httpmetric', () async {
       final HttpMetric httpMetric = performance.newHttpMetric(
-        'www.google.com',
+        'https://www.google.com',
         HttpMethod.Connect,
       );
 

From d6f25191769e53543cb037815dd73b880d892d1e Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 16:58:37 -0700
Subject: [PATCH 32/40] Temporarily remove integration tests

---
 packages/firebase_performance/example/lib/main.dart          | 1 -
 .../example/test_driver/firebase_performance.dart            | 5 ++---
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/packages/firebase_performance/example/lib/main.dart b/packages/firebase_performance/example/lib/main.dart
index 61e1ae39b6e7..16ed5b4322ee 100644
--- a/packages/firebase_performance/example/lib/main.dart
+++ b/packages/firebase_performance/example/lib/main.dart
@@ -77,7 +77,6 @@ class _MyAppState extends State<MyApp> {
     });
 
     final Trace trace = _performance.newTrace("test");
-
     trace.incrementMetric("metric1", 16);
     trace.putAttribute("favorite_color", "blue");
 
diff --git a/packages/firebase_performance/example/test_driver/firebase_performance.dart b/packages/firebase_performance/example/test_driver/firebase_performance.dart
index 295a5da94ad2..352db529bd1b 100644
--- a/packages/firebase_performance/example/test_driver/firebase_performance.dart
+++ b/packages/firebase_performance/example/test_driver/firebase_performance.dart
@@ -2,7 +2,6 @@ import 'dart:async';
 
 import 'package:flutter_driver/driver_extension.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:firebase_performance/firebase_performance.dart';
 
 void main() {
   final Completer<String> completer = Completer<String>();
@@ -10,6 +9,8 @@ void main() {
   tearDownAll(() => completer.complete(null));
 
   group('firebase_performance test driver', () {
+    // TODO(bparrishMines): Rewrite integration tests when iOS portion is written.
+    /*
     final FirebasePerformance performance = FirebasePerformance.instance;
 
     setUp(() async {
@@ -25,8 +26,6 @@ void main() {
       expect(disabled, isFalse);
     });
 
-    // TODO(bparrishMines): Rewrite integration test when iOS portion is written.
-    /*
     test('metric', () async {
       final Trace trace = performance.newTrace('test');
       trace.putAttribute('testAttribute', 'foo');

From 7f96745e5037ad29dc125655333d74dd111b4f5d Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Wed, 1 May 2019 17:04:12 -0700
Subject: [PATCH 33/40] Temporarily remove integration tests

---
 .../example/test_driver/firebase_performance.dart             | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/packages/firebase_performance/example/test_driver/firebase_performance.dart b/packages/firebase_performance/example/test_driver/firebase_performance.dart
index fcabfe11f239..352db529bd1b 100644
--- a/packages/firebase_performance/example/test_driver/firebase_performance.dart
+++ b/packages/firebase_performance/example/test_driver/firebase_performance.dart
@@ -2,7 +2,6 @@ import 'dart:async';
 
 import 'package:flutter_driver/driver_extension.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:firebase_performance/firebase_performance.dart';
 
 void main() {
   final Completer<String> completer = Completer<String>();
@@ -10,6 +9,8 @@ void main() {
   tearDownAll(() => completer.complete(null));
 
   group('firebase_performance test driver', () {
+    // TODO(bparrishMines): Rewrite integration tests when iOS portion is written.
+    /*
     final FirebasePerformance performance = FirebasePerformance.instance;
 
     setUp(() async {
@@ -37,5 +38,6 @@ void main() {
       expect(trace.getAttribute('testAttribute2'), null);
       expect(trace.getAttribute('testMetric'), null);
     });
+    */
   });
 }

From 52f04b8d3dcfabf53f909006f4afdad7be7d1904 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Sun, 5 May 2019 22:38:34 -0700
Subject: [PATCH 34/40] Make sharedInstance a constructor

---
 .../ios/Classes/FLTFirebasePerformance.m      | 20 ++++++++-----------
 .../ios/Classes/FirebasePerformancePlugin.h   |  3 +--
 .../ios/Classes/FirebasePerformancePlugin.m   |  5 ++++-
 3 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
index 7737df7d67a6..b8869e03d9f0 100644
--- a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -12,18 +12,14 @@ @implementation FLTFirebasePerformance
 + (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
 }
 
-+ (void)sharedInstanceWithCall:(FlutterMethodCall *)call result:(FlutterResult)result {
-  NSNumber *handle = call.arguments[@"handle"];
-  [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:[FLTFirebasePerformance new]];
-}
-
-- (instancetype)init {
-  self = [super init];
-  if (self) {
-    _performance = [FIRPerformance sharedInstance];
-  }
-
-  return self;
++ (instancetype _Nonnull)sharedInstance {
+  static FLTFirebasePerformance *sharedInstance = nil;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    sharedInstance = [[FLTFirebasePerformance alloc] init];
+    sharedInstance.performance = [FIRPerformance sharedInstance];
+  });
+  return sharedInstance;
 }
 
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index 3c45bd342866..17e20b5dfa21 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -8,8 +8,7 @@
 @end
 
 @interface FLTFirebasePerformance : NSObject <FlutterPlugin>
-+ (void)sharedInstanceWithCall:(FlutterMethodCall *_Nonnull)call
-                        result:(FlutterResult _Nonnull)result;
++ (instancetype _Nonnull)sharedInstance;
 @end
 
 @interface FLTTrace : NSObject <FlutterPlugin>
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index 82298f0ae970..a88409b01e6f 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -33,7 +33,10 @@ - (instancetype)init {
 
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
   if ([@"FirebasePerformance#instance" isEqualToString:call.method]) {
-    [FLTFirebasePerformance sharedInstanceWithCall:call result:result];
+    NSNumber *handle = call.arguments[@"handle"];
+    FLTFirebasePerformance performance = [FLTFirebasePerformance sharedInstance];
+
+    [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:performance];
     result(nil);
   } else {
     NSNumber *handle = call.arguments[@"handle"];

From fda650fed83d25b32845b3dea950bb0b805bd1b0 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bparr2450@gmail.com>
Date: Sun, 5 May 2019 23:28:53 -0700
Subject: [PATCH 35/40] Update FirebasePerformancePlugin.m

---
 .../ios/Classes/FirebasePerformancePlugin.m                     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index a88409b01e6f..606d683067bb 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -34,7 +34,7 @@ - (instancetype)init {
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
   if ([@"FirebasePerformance#instance" isEqualToString:call.method]) {
     NSNumber *handle = call.arguments[@"handle"];
-    FLTFirebasePerformance performance = [FLTFirebasePerformance sharedInstance];
+    FLTFirebasePerformance *performance = [FLTFirebasePerformance sharedInstance];
 
     [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:performance];
     result(nil);

From c02398541842b8af1e924307bab7647d8e4930cd Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bparr2450@gmail.com>
Date: Sun, 5 May 2019 23:30:09 -0700
Subject: [PATCH 36/40] Update FirebasePerformancePlugin.m

---
 .../ios/Classes/FirebasePerformancePlugin.m                     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index a88409b01e6f..606d683067bb 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -34,7 +34,7 @@ - (instancetype)init {
 - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
   if ([@"FirebasePerformance#instance" isEqualToString:call.method]) {
     NSNumber *handle = call.arguments[@"handle"];
-    FLTFirebasePerformance performance = [FLTFirebasePerformance sharedInstance];
+    FLTFirebasePerformance *performance = [FLTFirebasePerformance sharedInstance];
 
     [FLTFirebasePerformancePlugin addMethodHandler:handle methodHandler:performance];
     result(nil);

From 71ad2ea0b861e838b8d737c67c35a15637be64b2 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 7 May 2019 11:53:41 -0700
Subject: [PATCH 37/40] Create internal methods

---
 .../ios/Classes/FLTFirebasePerformance.m      |  2 +-
 .../ios/Classes/FLTHttpMetric.m               |  2 +-
 .../ios/Classes/FLTTrace.m                    |  2 +-
 .../FirebasePerformancePlugin+Internal.h      | 23 +++++++++++++++++++
 .../ios/Classes/FirebasePerformancePlugin.h   | 15 ------------
 .../ios/Classes/FirebasePerformancePlugin.m   |  2 +-
 6 files changed, 27 insertions(+), 19 deletions(-)
 create mode 100644 packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
index b8869e03d9f0..ab8a60b552fb 100644
--- a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#import "FirebasePerformancePlugin.h"
+#import "FirebasePerformancePlugin+Internal.h"
 
 @interface FLTFirebasePerformance ()
 @property FIRPerformance *performance;
diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
index 64a622aeb2d7..6140cb348d3f 100644
--- a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#import "FirebasePerformancePlugin.h"
+#import "FirebasePerformancePlugin+Internal.h"
 
 @interface FLTHttpMetric ()
 @property FIRHTTPMetric *metric;
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
index a522e3d38a39..f4baa6ba2738 100644
--- a/packages/firebase_performance/ios/Classes/FLTTrace.m
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#import "FirebasePerformancePlugin.h"
+#import "FirebasePerformancePlugin+Internal.h"
 
 @interface FLTTrace ()
 @property FIRTrace *trace;
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h
new file mode 100644
index 000000000000..8c25eeec53fd
--- /dev/null
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h
@@ -0,0 +1,23 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "FirebasePerformancePlugin.h"
+
+@interface FLTFirebasePerformancePlugin (Internal)
++ (void)addMethodHandler:(NSNumber *_Nonnull)handle
+           methodHandler:(id<FlutterPlugin> _Nonnull)handler;
++ (void)removeMethodHandler:(NSNumber *_Nonnull)handle;
+@end
+
+@interface FLTFirebasePerformance : NSObject <FlutterPlugin>
++ (instancetype _Nonnull)sharedInstance;
+@end
+
+@interface FLTTrace : NSObject <FlutterPlugin>
+- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
+@end
+
+@interface FLTHttpMetric : NSObject <FlutterPlugin>
+- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric;
+@end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
index 17e20b5dfa21..44bf53592eb9 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.h
@@ -2,19 +2,4 @@
 #import <Flutter/Flutter.h>
 
 @interface FLTFirebasePerformancePlugin : NSObject <FlutterPlugin>
-+ (void)addMethodHandler:(NSNumber *_Nonnull)handle
-           methodHandler:(id<FlutterPlugin> _Nonnull)handler;
-+ (void)removeMethodHandler:(NSNumber *_Nonnull)handle;
-@end
-
-@interface FLTFirebasePerformance : NSObject <FlutterPlugin>
-+ (instancetype _Nonnull)sharedInstance;
-@end
-
-@interface FLTTrace : NSObject <FlutterPlugin>
-- (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
-@end
-
-@interface FLTHttpMetric : NSObject <FlutterPlugin>
-- (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric;
 @end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index 606d683067bb..2c2c8fa7efcf 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#import "FirebasePerformancePlugin.h"
+#import "FirebasePerformancePlugin+Internal.h"
 
 @implementation FLTFirebasePerformancePlugin
 static NSMutableDictionary<NSNumber *, id<FlutterPlugin>> *methodHandlers;

From 58f736d51e8908beb35a84c5e10fe6b31adcb813 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Tue, 7 May 2019 12:12:54 -0700
Subject: [PATCH 38/40] testin

---
 packages/firebase_performance/example/pubspec.yaml            | 2 --
 .../example/test_driver/firebase_performance.dart             | 4 +---
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/packages/firebase_performance/example/pubspec.yaml b/packages/firebase_performance/example/pubspec.yaml
index ef9440d129f5..2c6ba939aa4b 100644
--- a/packages/firebase_performance/example/pubspec.yaml
+++ b/packages/firebase_performance/example/pubspec.yaml
@@ -17,7 +17,5 @@ dev_dependencies:
     sdk: flutter
   test: any
 
-
-
 flutter:
   uses-material-design: true
diff --git a/packages/firebase_performance/example/test_driver/firebase_performance.dart b/packages/firebase_performance/example/test_driver/firebase_performance.dart
index 3e52f2f4583b..ae6d62069690 100644
--- a/packages/firebase_performance/example/test_driver/firebase_performance.dart
+++ b/packages/firebase_performance/example/test_driver/firebase_performance.dart
@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:flutter_driver/driver_extension.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:firebase_performance/firebase_performance.dart';
 
 void main() {
   final Completer<String> completer = Completer<String>();
@@ -9,8 +10,6 @@ void main() {
   tearDownAll(() => completer.complete(null));
 
   group('firebase_performance test driver', () {
-    // TODO(bparrishMines): Rewrite integration tests when iOS portion is written.
-    /*
     final FirebasePerformance performance = FirebasePerformance.instance;
 
     setUp(() async {
@@ -65,6 +64,5 @@ void main() {
 
       await httpMetric.stop();
     });
-    */
   });
 }

From 21a67f8f7c4bebb00c46e52861f50e984500a1ef Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Thu, 9 May 2019 13:11:53 -0700
Subject: [PATCH 39/40] Use MethodCallHandler protocol

---
 .../ios/Classes/FLTFirebasePerformance.m            |  3 ---
 .../ios/Classes/FLTHttpMetric.m                     |  3 ---
 .../firebase_performance/ios/Classes/FLTTrace.m     |  3 ---
 .../Classes/FirebasePerformancePlugin+Internal.h    | 13 +++++++++----
 .../ios/Classes/FirebasePerformancePlugin.m         |  4 ++--
 5 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
index ab8a60b552fb..81cf29c06559 100644
--- a/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
+++ b/packages/firebase_performance/ios/Classes/FLTFirebasePerformance.m
@@ -9,9 +9,6 @@ @interface FLTFirebasePerformance ()
 @end
 
 @implementation FLTFirebasePerformance
-+ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
-}
-
 + (instancetype _Nonnull)sharedInstance {
   static FLTFirebasePerformance *sharedInstance = nil;
   static dispatch_once_t onceToken;
diff --git a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
index 6140cb348d3f..3a12f3400613 100644
--- a/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
+++ b/packages/firebase_performance/ios/Classes/FLTHttpMetric.m
@@ -9,9 +9,6 @@ @interface FLTHttpMetric ()
 @end
 
 @implementation FLTHttpMetric
-+ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
-}
-
 - (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *)metric {
   self = [self init];
   if (self) {
diff --git a/packages/firebase_performance/ios/Classes/FLTTrace.m b/packages/firebase_performance/ios/Classes/FLTTrace.m
index f4baa6ba2738..3ce6af5fc3ef 100644
--- a/packages/firebase_performance/ios/Classes/FLTTrace.m
+++ b/packages/firebase_performance/ios/Classes/FLTTrace.m
@@ -9,9 +9,6 @@ @interface FLTTrace ()
 @end
 
 @implementation FLTTrace
-+ (void)registerWithRegistrar:(nonnull NSObject<FlutterPluginRegistrar> *)registrar {
-}
-
 - (instancetype _Nonnull)initWithTrace:(FIRTrace *)trace {
   self = [self init];
   if (self) {
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h
index 8c25eeec53fd..f0adca5b905b 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin+Internal.h
@@ -4,20 +4,25 @@
 
 #import "FirebasePerformancePlugin.h"
 
+@protocol MethodCallHandler
+@required
+- (void)handleMethodCall:(FlutterMethodCall *_Nonnull)call result:(FlutterResult _Nonnull)result;
+@end
+
 @interface FLTFirebasePerformancePlugin (Internal)
 + (void)addMethodHandler:(NSNumber *_Nonnull)handle
-           methodHandler:(id<FlutterPlugin> _Nonnull)handler;
+           methodHandler:(id<MethodCallHandler> _Nonnull)handler;
 + (void)removeMethodHandler:(NSNumber *_Nonnull)handle;
 @end
 
-@interface FLTFirebasePerformance : NSObject <FlutterPlugin>
+@interface FLTFirebasePerformance : NSObject <MethodCallHandler>
 + (instancetype _Nonnull)sharedInstance;
 @end
 
-@interface FLTTrace : NSObject <FlutterPlugin>
+@interface FLTTrace : NSObject <MethodCallHandler>
 - (instancetype _Nonnull)initWithTrace:(FIRTrace *_Nonnull)trace;
 @end
 
-@interface FLTHttpMetric : NSObject <FlutterPlugin>
+@interface FLTHttpMetric : NSObject <MethodCallHandler>
 - (instancetype _Nonnull)initWithHTTPMetric:(FIRHTTPMetric *_Nonnull)metric;
 @end
diff --git a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
index 2c2c8fa7efcf..1c387265c988 100644
--- a/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
+++ b/packages/firebase_performance/ios/Classes/FirebasePerformancePlugin.m
@@ -5,7 +5,7 @@
 #import "FirebasePerformancePlugin+Internal.h"
 
 @implementation FLTFirebasePerformancePlugin
-static NSMutableDictionary<NSNumber *, id<FlutterPlugin>> *methodHandlers;
+static NSMutableDictionary<NSNumber *, id<MethodCallHandler>> *methodHandlers;
 
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   methodHandlers = [NSMutableDictionary new];
@@ -49,7 +49,7 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
   }
 }
 
-+ (void)addMethodHandler:(NSNumber *)handle methodHandler:(id<FlutterPlugin>)handler {
++ (void)addMethodHandler:(NSNumber *)handle methodHandler:(id<MethodCallHandler>)handler {
   if (methodHandlers[handle]) {
     NSString *reason =
         [[NSString alloc] initWithFormat:@"Object for handle already exists: %d", handle.intValue];

From a04ef6ad7801a69e216398e425ede3c5098dc525 Mon Sep 17 00:00:00 2001
From: Maurice Parrish <bmparr@google.com>
Date: Thu, 9 May 2019 13:37:58 -0700
Subject: [PATCH 40/40] Add note about leaking

---
 packages/firebase_performance/lib/src/http_metric.dart | 5 ++++-
 packages/firebase_performance/lib/src/trace.dart       | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index a9f54830790b..c0b27bb41ce3 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -8,13 +8,16 @@ part of firebase_performance;
 ///
 /// It is possible to have more than one [HttpMetric] running at a time.
 /// Attributes can also be added to help measure performance related events. A
-/// [HttpMetric] also measures the time between calling start() and stop().
+/// [HttpMetric] also measures the time between calling `start()` and `stop()`.
 ///
 /// Data collected is automatically sent to the associated Firebase console
 /// after stop() is called.
 ///
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
+///
+/// It is highly recommended that one always calls `start()` and `stop()` on
+/// each created [HttpMetric] to avoid leaking on the platform side.
 class HttpMetric extends PerformanceAttributes {
   HttpMetric._(this._handle, this.url, this.httpMethod);
 
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index f77e0f7a3683..cf8e1fb01d3a 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -11,13 +11,16 @@ part of firebase_performance;
 /// possible to have more than one custom trace running at a time. Each custom
 /// trace can have multiple metrics and attributes added to help measure
 /// performance related events. A trace also measures the time between calling
-/// start() and stop().
+/// `start()` and `stop()`.
 ///
 /// Data collected is automatically sent to the associated Firebase console
 /// after stop() is called.
 ///
 /// You can confirm that Performance Monitoring results appear in the Firebase
 /// console. Results should appear within 12 hours.
+///
+/// It is highly recommended that one always calls `start()` and `stop()` on
+/// each created [Trace] to not avoid leaking on the platform side.
 class Trace extends PerformanceAttributes {
   Trace._(this._handle, this.name);