From f374f86af1d4f8281c2d7af01b943918fe910791 Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Mon, 21 Oct 2019 15:55:44 -0700
Subject: [PATCH 1/9] Add Firefox installing functionality to test platform.
 For Linux only. Refactor test platform code

---
 lib/web_ui/dev/browser.dart           | 140 +++++++++++++++
 lib/web_ui/dev/chrome.dart            |  82 +++++++++
 lib/web_ui/dev/common.dart            |  62 ++++---
 lib/web_ui/dev/download.dart          |  28 +++
 lib/web_ui/dev/felt.dart              |   4 +-
 lib/web_ui/dev/firefox.dart           |  82 +++++++++
 lib/web_ui/dev/firefox_installer.dart |  81 ++++++++-
 lib/web_ui/dev/test_platform.dart     | 241 +-------------------------
 lib/web_ui/dev/test_runner.dart       |   1 +
 9 files changed, 459 insertions(+), 262 deletions(-)
 create mode 100644 lib/web_ui/dev/browser.dart
 create mode 100644 lib/web_ui/dev/chrome.dart
 create mode 100644 lib/web_ui/dev/download.dart
 create mode 100644 lib/web_ui/dev/firefox.dart

diff --git a/lib/web_ui/dev/browser.dart b/lib/web_ui/dev/browser.dart
new file mode 100644
index 0000000000000..852ec335f9134
--- /dev/null
+++ b/lib/web_ui/dev/browser.dart
@@ -0,0 +1,140 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:pedantic/pedantic.dart';
+import 'package:stack_trace/stack_trace.dart';
+import 'package:typed_data/typed_buffers.dart';
+
+import 'package:test_api/src/utils.dart'; // ignore: implementation_imports
+
+/// An interface for running browser instances.
+///
+/// This is intentionally coarse-grained: browsers are controlled primary from
+/// inside a single tab. Thus this interface only provides support for closing
+/// the browser and seeing if it closes itself.
+///
+/// Any errors starting or running the browser process are reported through
+/// [onExit].
+abstract class Browser {
+  String get name;
+
+  /// The Observatory URL for this browser.
+  ///
+  /// This will return `null` for browsers that aren't running the Dart VM, or
+  /// if the Observatory URL can't be found.
+  Future<Uri> get observatoryUrl => null;
+
+  /// The remote debugger URL for this browser.
+  ///
+  /// This will return `null` for browsers that don't support remote debugging,
+  /// or if the remote debugging URL can't be found.
+  Future<Uri> get remoteDebuggerUrl => null;
+
+  /// The underlying process.
+  ///
+  /// This will fire once the process has started successfully.
+  Future<Process> get _process => _processCompleter.future;
+  final _processCompleter = Completer<Process>();
+
+  /// Whether [close] has been called.
+  var _closed = false;
+
+  /// A future that completes when the browser exits.
+  ///
+  /// If there's a problem starting or running the browser, this will complete
+  /// with an error.
+  Future get onExit => _onExitCompleter.future;
+  final _onExitCompleter = Completer();
+
+  /// Standard IO streams for the underlying browser process.
+  final _ioSubscriptions = <StreamSubscription>[];
+
+  /// Creates a new browser.
+  ///
+  /// This is intended to be called by subclasses. They pass in [startBrowser],
+  /// which asynchronously returns the browser process. Any errors in
+  /// [startBrowser] (even those raised asynchronously after it returns) are
+  /// piped to [onExit] and will cause the browser to be killed.
+  Browser(Future<Process> startBrowser()) {
+    // Don't return a Future here because there's no need for the caller to wait
+    // for the process to actually start. They should just wait for the HTTP
+    // request instead.
+    runZoned(() async {
+      var process = await startBrowser();
+      _processCompleter.complete(process);
+
+      var output = Uint8Buffer();
+      drainOutput(Stream<List<int>> stream) {
+        try {
+          _ioSubscriptions
+              .add(stream.listen(output.addAll, cancelOnError: true));
+        } on StateError catch (_) {}
+      }
+
+      // If we don't drain the stdout and stderr the process can hang.
+      drainOutput(process.stdout);
+      drainOutput(process.stderr);
+
+      var exitCode = await process.exitCode;
+
+      // This hack dodges an otherwise intractable race condition. When the user
+      // presses Control-C, the signal is sent to the browser and the test
+      // runner at the same time. It's possible for the browser to exit before
+      // the [Browser.close] is called, which would trigger the error below.
+      //
+      // A negative exit code signals that the process exited due to a signal.
+      // However, it's possible that this signal didn't come from the user's
+      // Control-C, in which case we do want to throw the error. The only way to
+      // resolve the ambiguity is to wait a brief amount of time and see if this
+      // browser is actually closed.
+      if (!_closed && exitCode < 0) {
+        await Future.delayed(Duration(milliseconds: 200));
+      }
+
+      if (!_closed && exitCode != 0) {
+        var outputString = utf8.decode(output);
+        var message = '$name failed with exit code $exitCode.';
+        if (outputString.isNotEmpty) {
+          message += '\nStandard output:\n$outputString';
+        }
+
+        throw Exception(message);
+      }
+
+      _onExitCompleter.complete();
+    }, onError: (error, StackTrace stackTrace) {
+      // Ignore any errors after the browser has been closed.
+      if (_closed) return;
+
+      // Make sure the process dies even if the error wasn't fatal.
+      _process.then((process) => process.kill());
+
+      if (stackTrace == null) stackTrace = Trace.current();
+      if (_onExitCompleter.isCompleted) return;
+      _onExitCompleter.completeError(
+          Exception('Failed to run $name: ${getErrorMessage(error)}.'),
+          stackTrace);
+    });
+  }
+
+  /// Kills the browser process.
+  ///
+  /// Returns the same [Future] as [onExit], except that it won't emit
+  /// exceptions.
+  Future close() async {
+    _closed = true;
+
+    // If we don't manually close the stream the test runner can hang.
+    // For example this happens with Chrome Headless.
+    // See SDK issue: https://github.com/dart-lang/sdk/issues/31264
+    for (var stream in _ioSubscriptions) {
+      unawaited(stream.cancel());
+    }
+
+    (await _process).kill();
+
+    // Swallow exceptions. The user should explicitly use [onExit] for these.
+    return onExit.catchError((_) {});
+  }
+}
diff --git a/lib/web_ui/dev/chrome.dart b/lib/web_ui/dev/chrome.dart
new file mode 100644
index 0000000000000..6f895833ff948
--- /dev/null
+++ b/lib/web_ui/dev/chrome.dart
@@ -0,0 +1,82 @@
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:pedantic/pedantic.dart';
+
+import 'package:test_core/src/util/io.dart'; // ignore: implementation_imports
+
+import 'browser.dart';
+import 'chrome_installer.dart';
+import 'common.dart';
+
+/// A class for running an instance of Chrome.
+///
+/// Most of the communication with the browser is expected to happen via HTTP,
+/// so this exposes a bare-bones API. The browser starts as soon as the class is
+/// constructed, and is killed when [close] is called.
+///
+/// Any errors starting or running the process are reported through [onExit].
+class Chrome extends Browser {
+  @override
+  final name = 'Chrome';
+
+  @override
+  final Future<Uri> remoteDebuggerUrl;
+
+  static String version;
+
+  /// Starts a new instance of Chrome open to the given [url], which may be a
+  /// [Uri] or a [String].
+  factory Chrome(Uri url, {bool debug = false}) {
+    assert(version != null);
+    var remoteDebuggerCompleter = Completer<Uri>.sync();
+    return Chrome._(() async {
+      final BrowserInstallation installation = await getOrInstallChrome(
+        version,
+        infoLog: isCirrus ? stdout : DevNull(),
+      );
+
+      // A good source of various Chrome CLI options:
+      // https://peter.sh/experiments/chromium-command-line-switches/
+      //
+      // Things to try:
+      // --font-render-hinting
+      // --enable-font-antialiasing
+      // --gpu-rasterization-msaa-sample-count
+      // --disable-gpu
+      // --disallow-non-exact-resource-reuse
+      // --disable-font-subpixel-positioning
+      final bool isChromeNoSandbox = Platform.environment['CHROME_NO_SANDBOX'] == 'true';
+      var dir = createTempDir();
+      var args = [
+        '--user-data-dir=$dir',
+        url.toString(),
+        if (!debug) '--headless',
+        if (isChromeNoSandbox) '--no-sandbox',
+        '--window-size=$kMaxScreenshotWidth,$kMaxScreenshotHeight', // When headless, this is the actual size of the viewport
+        '--disable-extensions',
+        '--disable-popup-blocking',
+        '--bwsi',
+        '--no-first-run',
+        '--no-default-browser-check',
+        '--disable-default-apps',
+        '--disable-translate',
+        '--remote-debugging-port=$kDevtoolsPort',
+      ];
+
+      final Process process = await Process.start(installation.executable, args);
+
+      remoteDebuggerCompleter.complete(getRemoteDebuggerUrl(
+          Uri.parse('http://localhost:${kDevtoolsPort}')));
+
+      unawaited(process.exitCode
+          .then((_) => Directory(dir).deleteSync(recursive: true)));
+
+      return process;
+    }, remoteDebuggerCompleter.future);
+  }
+
+  Chrome._(Future<Process> startBrowser(), this.remoteDebuggerUrl)
+      : super(startBrowser);
+}
diff --git a/lib/web_ui/dev/common.dart b/lib/web_ui/dev/common.dart
index 99d764b08e060..e96872da283c5 100644
--- a/lib/web_ui/dev/common.dart
+++ b/lib/web_ui/dev/common.dart
@@ -8,6 +8,12 @@ import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 import 'package:yaml/yaml.dart';
 
+/// The port number for debugging.
+const int kDevtoolsPort = 12345;
+const int kMaxScreenshotWidth = 1024;
+const int kMaxScreenshotHeight = 1024;
+const double kMaxDiffRateFailure = 0.28 / 100; // 0.28%
+
 class BrowserInstallerException implements Exception {
   BrowserInstallerException(this.message);
 
@@ -60,20 +66,16 @@ class _LinuxBinding implements PlatformBinding {
       path.join(versionDir.path, 'chrome-linux', 'chrome');
 
   @override
-  String getFirefoxDownloadUrl(String version) {
-    return 'https://download-installer.cdn.mozilla.net/pub/firefox/releases/${version}/linux-x86_64/en-US/firefox-${version}.tar.bz2';
-  }
+  String getFirefoxDownloadUrl(String version) =>
+      'https://download-installer.cdn.mozilla.net/pub/firefox/releases/${version}/linux-x86_64/en-US/firefox-${version}.tar.bz2';
 
   @override
-  String getFirefoxExecutablePath(io.Directory versionDir) {
-    // TODO: implement getFirefoxExecutablePath
-    return null;
-  }
+  String getFirefoxExecutablePath(io.Directory versionDir) =>
+      path.join(versionDir.path, 'firefox', 'firefox');
 
   @override
-  String getFirefoxLatestVersionUrl() {
-    return 'https://download.mozilla.org/?product=firefox-latest&os=linux64&lang=en-US';
-  }
+  String getFirefoxLatestVersionUrl() =>
+      'https://download.mozilla.org/?product=firefox-latest&os=linux64&lang=en-US';
 }
 
 class _MacBinding implements PlatformBinding {
@@ -87,7 +89,6 @@ class _MacBinding implements PlatformBinding {
   String getChromeDownloadUrl(String version) =>
       '$_kBaseDownloadUrl/Mac%2F$version%2Fchrome-mac.zip?alt=media';
 
-  @override
   String getChromeExecutablePath(io.Directory versionDir) => path.join(
       versionDir.path,
       'chrome-mac',
@@ -97,28 +98,24 @@ class _MacBinding implements PlatformBinding {
       'Chromium');
 
   @override
-  String getFirefoxDownloadUrl(String version) {
-    // TODO: implement getFirefoxDownloadUrl
-    return null;
-  }
+  String getFirefoxDownloadUrl(String version) =>
+      'https://download-installer.cdn.mozilla.net/pub/firefox/releases/${version}/mac/en-US/firefox-${version}.dmg';
 
   @override
   String getFirefoxExecutablePath(io.Directory versionDir) {
-    // TODO: implement getFirefoxExecutablePath
-    return null;
+    throw UnimplementedError();
   }
 
   @override
-  String getFirefoxLatestVersionUrl() {
-    return 'https://download.mozilla.org/?product=firefox-latest&os=osx&lang=en-US';
-  }
+  String getFirefoxLatestVersionUrl() =>
+      'https://download.mozilla.org/?product=firefox-latest&os=osx&lang=en-US';
 }
 
 class BrowserInstallation {
-  const BrowserInstallation({
-    @required this.version,
-    @required this.executable,
-  });
+  const BrowserInstallation(
+      {@required this.version,
+      @required this.executable,
+      fetchLatestChromeVersion});
 
   /// Browser version.
   final String version;
@@ -126,3 +123,20 @@ class BrowserInstallation {
   /// Path the the browser executable.
   final String executable;
 }
+
+/// A string sink that swallows all input.
+class DevNull implements StringSink {
+  @override
+  void write(Object obj) {}
+
+  @override
+  void writeAll(Iterable objects, [String separator = ""]) {}
+
+  @override
+  void writeCharCode(int charCode) {}
+
+  @override
+  void writeln([Object obj = ""]) {}
+}
+
+bool get isCirrus => io.Platform.environment['CIRRUS_CI'] == 'true';
diff --git a/lib/web_ui/dev/download.dart b/lib/web_ui/dev/download.dart
new file mode 100644
index 0000000000000..57f708177f896
--- /dev/null
+++ b/lib/web_ui/dev/download.dart
@@ -0,0 +1,28 @@
+// Copyright 2013 The Flutter 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 'dart:async';
+
+import 'package:args/command_runner.dart';
+
+import 'common.dart';
+import 'firefox_installer.dart';
+
+class DownloadCommand extends Command<bool> {
+  DownloadCommand();
+
+  @override
+  String get name => 'download';
+
+  @override
+  String get description => 'Deletes build caches and artifacts.';
+
+  @override
+  FutureOr<bool> run() async {
+    BrowserInstallation installation = await getOrInstallFirefox('69.0.2');
+
+    print('Firefox installed: ${installation.version}');
+    print('Firefox installed: ${installation.executable}');
+  }
+}
diff --git a/lib/web_ui/dev/felt.dart b/lib/web_ui/dev/felt.dart
index 1830c051b9ef6..172d9444916e8 100644
--- a/lib/web_ui/dev/felt.dart
+++ b/lib/web_ui/dev/felt.dart
@@ -8,6 +8,7 @@ import 'package:args/command_runner.dart';
 
 import 'build.dart';
 import 'clean.dart';
+import 'download.dart';
 import 'licenses.dart';
 import 'test_runner.dart';
 
@@ -18,7 +19,8 @@ CommandRunner runner = CommandRunner<bool>(
   ..addCommand(CleanCommand())
   ..addCommand(LicensesCommand())
   ..addCommand(TestCommand())
-  ..addCommand(BuildCommand());
+  ..addCommand(BuildCommand())
+  ..addCommand(DownloadCommand());
 
 void main(List<String> args) async {
   if (args.isEmpty) {
diff --git a/lib/web_ui/dev/firefox.dart b/lib/web_ui/dev/firefox.dart
new file mode 100644
index 0000000000000..d63d9a524ca81
--- /dev/null
+++ b/lib/web_ui/dev/firefox.dart
@@ -0,0 +1,82 @@
+
+// import 'dart:async';
+// import 'dart:io';
+
+// import 'package:pedantic/pedantic.dart';
+
+// import 'package:test_core/src/util/io.dart'; // ignore: implementation_imports
+
+// import 'browser.dart';
+// import 'firefox_installer.dart';
+// import 'common.dart';
+
+// /// A class for running an instance of Firefox.
+// ///
+// /// Most of the communication with the browser is expected to happen via HTTP,
+// /// so this exposes a bare-bones API. The browser starts as soon as the class is
+// /// constructed, and is killed when [close] is called.
+// ///
+// /// Any errors starting or running the process are reported through [onExit].
+// class Firefox extends Browser {
+//   @override
+//   final name = 'Firefox';
+
+//   @override
+//   final Future<Uri> remoteDebuggerUrl;
+
+//   static String version;
+
+//   /// Starts a new instance of Firefox open to the given [url], which may be a
+//   /// [Uri] or a [String].
+//   factory Firefox(Uri url, {bool debug = false}) {
+//     assert(version != null);
+//     var remoteDebuggerCompleter = Completer<Uri>.sync();
+//     return Firefox._(() async {
+//       final BrowserInstallation installation = await getOrInstallFirefox(
+//         version,
+//         infoLog: isCirrus ? stdout : DevNull(),
+//       );
+
+//       // A good source of various Firefox CLI options:
+//       // https://peter.sh/experiments/chromium-command-line-switches/
+//       //
+//       // Things to try:
+//       // --font-render-hinting
+//       // --enable-font-antialiasing
+//       // --gpu-rasterization-msaa-sample-count
+//       // --disable-gpu
+//       // --disallow-non-exact-resource-reuse
+//       // --disable-font-subpixel-positioning
+//       final bool isFirefoxNoSandbox = Platform.environment['CHROME_NO_SANDBOX'] == 'true';
+//       var dir = createTempDir();
+//       var args = [
+//         '--user-data-dir=$dir',
+//         url.toString(),
+//         if (!debug) '--headless',
+//         if (isFirefoxNoSandbox) '--no-sandbox',
+//         '--window-size=$kMaxScreenshotWidth,$kMaxScreenshotHeight', // When headless, this is the actual size of the viewport
+//         '--disable-extensions',
+//         '--disable-popup-blocking',
+//         '--bwsi',
+//         '--no-first-run',
+//         '--no-default-browser-check',
+//         '--disable-default-apps',
+//         '--disable-translate',
+//         '--remote-debugging-port=$kDevtoolsPort',
+//       ];
+
+//       final Process process = await Process.start(installation.executable, args);
+
+//       remoteDebuggerCompleter.complete(getRemoteDebuggerUrl(
+//           Uri.parse('http://localhost:$_kFirefoxDevtoolsPort')));
+
+//       unawaited(process.exitCode
+//           .then((_) => Directory(dir).deleteSync(recursive: true)));
+
+//       return process;
+//     }, remoteDebuggerCompleter.future);
+//   }
+
+//   Firefox._(Future<Process> startBrowser(), this.remoteDebuggerUrl)
+//       : super(startBrowser);
+// }
diff --git a/lib/web_ui/dev/firefox_installer.dart b/lib/web_ui/dev/firefox_installer.dart
index ccf7a7e0d8eb9..14c6bcc4a145e 100644
--- a/lib/web_ui/dev/firefox_installer.dart
+++ b/lib/web_ui/dev/firefox_installer.dart
@@ -10,6 +10,59 @@ import 'package:path/path.dart' as path;
 import 'common.dart';
 import 'environment.dart';
 
+/// Returns the installation of Firefox, installing it if necessary.
+///
+/// If [requestedVersion] is null, uses the version specified on the
+/// command-line. If not specified on the command-line, uses the version
+/// specified in the "browser_lock.yaml" file.
+///
+/// If [requestedVersion] is not null, installs that version. The value
+/// may be "latest" (the latest stable Firefox version), "system"
+/// (manually installed Firefox on the current operating system), or an
+/// exact version number such as 69.0.3. Versions of Firefox can be found here:
+///
+/// https://download-installer.cdn.mozilla.net/pub/firefox/releases/
+Future<BrowserInstallation> getOrInstallFirefox(
+  String requestedVersion, {
+  StringSink infoLog,
+}) async {
+
+  // Installation support is implemented only for Linux for now.
+  if(!io.Platform.isLinux) {
+    throw UnimplementedError();
+  }
+
+  infoLog ??= io.stdout;
+
+  if (requestedVersion == 'system') {
+    return BrowserInstallation(
+      version: 'system',
+      executable: await _findSystemFirefoxExecutable(),
+    );
+  }
+
+  FirefoxInstaller installer;
+  try {
+    installer = requestedVersion == 'latest'
+        ? await FirefoxInstaller.latest()
+        : FirefoxInstaller(version: requestedVersion);
+
+    if (installer.isInstalled) {
+      infoLog.writeln(
+          'Installation was skipped because Firefox version ${installer.version} is already installed.');
+    } else {
+      infoLog.writeln('Installing Firefox version: ${installer.version}');
+      await installer.install();
+      final BrowserInstallation installation = installer.getInstallation();
+      infoLog.writeln(
+          'Installations complete. To launch it run ${installation.executable}');
+    }
+    return installer.getInstallation();
+  } finally {
+    installer?.close();
+  }
+}
+
 /// Manages the installation of a particular [version] of Firefox.
 class FirefoxInstaller {
   factory FirefoxInstaller({
@@ -96,7 +149,7 @@ class FirefoxInstaller {
     ));
 
     final io.File downloadedFile =
-        io.File(path.join(versionDir.path, 'firefox.zip'));
+        io.File(path.join(versionDir.path, 'firefox-${version}.tar.bz2'));
     await download.stream.pipe(downloadedFile.openWrite());
 
     return downloadedFile;
@@ -105,7 +158,19 @@ class FirefoxInstaller {
   /// Uncompress the downloaded browser files.
   /// See [version].
   Future<void> _uncompress(io.File downloadedFile) async {
-    /// TODO(nturgut): Implement Install.
+    final io.ProcessResult unzipResult = await io.Process.run('tar', <String>[
+      '-x',
+      '-f',
+      downloadedFile.path,
+      '-C',
+      versionDir.path,
+    ]);
+
+    if (unzipResult.exitCode != 0) {
+      throw BrowserInstallerException(
+          'Failed to unzip the downloaded Firefox archive ${downloadedFile.path}.\n'
+          'The unzip process exited with code ${unzipResult.exitCode}.');
+    }
   }
 
   void close() {
@@ -113,6 +178,18 @@ class FirefoxInstaller {
   }
 }
 
+Future<String> _findSystemFirefoxExecutable() async {
+  final io.ProcessResult which =
+      await io.Process.run('which', <String>['firefox']);
+
+  if (which.exitCode != 0) {
+    throw BrowserInstallerException(
+        'Failed to locate system Firefox installation.');
+  }
+
+  return which.stdout;
+}
+
 /// Fetches the latest available Chrome build version.
 Future<String> fetchLatestFirefoxVersion() async {
   final RegExp forFirefoxVersion = RegExp("firefox-[0-9.]\+[0-9]");
diff --git a/lib/web_ui/dev/test_platform.dart b/lib/web_ui/dev/test_platform.dart
index 99236d759b8f5..bf1b5f95614d0 100644
--- a/lib/web_ui/dev/test_platform.dart
+++ b/lib/web_ui/dev/test_platform.dart
@@ -12,16 +12,13 @@ import 'package:http_multi_server/http_multi_server.dart';
 import 'package:image/image.dart';
 import 'package:package_resolver/package_resolver.dart';
 import 'package:path/path.dart' as p;
-import 'package:pedantic/pedantic.dart';
 import 'package:pool/pool.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;
 import 'package:shelf_static/shelf_static.dart';
 import 'package:shelf_web_socket/shelf_web_socket.dart';
 import 'package:shelf_packages_handler/shelf_packages_handler.dart';
-import 'package:stack_trace/stack_trace.dart';
 import 'package:stream_channel/stream_channel.dart';
-import 'package:typed_data/typed_buffers.dart';
 import 'package:web_socket_channel/web_socket_channel.dart';
 
 import 'package:test_api/src/backend/runtime.dart'; // ignore: implementation_imports
@@ -40,17 +37,12 @@ import 'package:test_core/src/runner/load_exception.dart'; // ignore: implementa
 import 'package:webkit_inspection_protocol/webkit_inspection_protocol.dart'
     as wip;
 
-import 'chrome_installer.dart';
+import 'browser.dart';
+import 'chrome.dart';
 import 'common.dart';
 import 'environment.dart' as env;
 import 'goldens.dart';
 
-/// The port number Chrome exposes for debugging.
-const int _kChromeDevtoolsPort = 12345;
-const int _kMaxScreenshotWidth = 1024;
-const int _kMaxScreenshotHeight = 1024;
-const double _kMaxDiffRateFailure = 0.28/100; // 0.28%
-
 class BrowserPlatform extends PlatformPlugin {
   /// Starts the server.
   ///
@@ -149,7 +141,7 @@ class BrowserPlatform extends PlatformPlugin {
     final bool write = requestData['write'];
     final double maxDiffRate = requestData['maxdiffrate'];
     final Map<String, dynamic> region = requestData['region'];
-    final String result = await _diffScreenshot(filename, write, maxDiffRate ?? _kMaxDiffRateFailure, region);
+    final String result = await _diffScreenshot(filename, write, maxDiffRate ?? kMaxDiffRateFailure, region);
     return shelf.Response.ok(json.encode(result));
   }
 
@@ -189,7 +181,7 @@ To automatically create this file call matchGoldenFile('$filename', write: true)
     }
 
     final wip.ChromeConnection chromeConnection =
-        wip.ChromeConnection('localhost', _kChromeDevtoolsPort);
+        wip.ChromeConnection('localhost', kDevtoolsPort);
     final wip.ChromeTab chromeTab = await chromeConnection.getTab(
         (wip.ChromeTab chromeTab) => chromeTab.url.contains('localhost'));
     final wip.WipConnection wipConnection = await chromeTab.connect();
@@ -211,8 +203,8 @@ To automatically create this file call matchGoldenFile('$filename', write: true)
     // Setting hardware-independent screen parameters:
     // https://chromedevtools.github.io/devtools-protocol/tot/Emulation
     await wipConnection.sendCommand('Emulation.setDeviceMetricsOverride', {
-      'width': _kMaxScreenshotWidth,
-      'height': _kMaxScreenshotHeight,
+      'width': kMaxScreenshotWidth,
+      'height': kMaxScreenshotHeight,
       'deviceScaleFactor': 1,
       'mobile': false,
     });
@@ -840,225 +832,4 @@ class _BrowserEnvironment implements Environment {
   CancelableOperation displayPause() => _manager._displayPause();
 }
 
-/// An interface for running browser instances.
-///
-/// This is intentionally coarse-grained: browsers are controlled primary from
-/// inside a single tab. Thus this interface only provides support for closing
-/// the browser and seeing if it closes itself.
-///
-/// Any errors starting or running the browser process are reported through
-/// [onExit].
-abstract class Browser {
-  String get name;
-
-  /// The Observatory URL for this browser.
-  ///
-  /// This will return `null` for browsers that aren't running the Dart VM, or
-  /// if the Observatory URL can't be found.
-  Future<Uri> get observatoryUrl => null;
-
-  /// The remote debugger URL for this browser.
-  ///
-  /// This will return `null` for browsers that don't support remote debugging,
-  /// or if the remote debugging URL can't be found.
-  Future<Uri> get remoteDebuggerUrl => null;
-
-  /// The underlying process.
-  ///
-  /// This will fire once the process has started successfully.
-  Future<Process> get _process => _processCompleter.future;
-  final _processCompleter = Completer<Process>();
-
-  /// Whether [close] has been called.
-  var _closed = false;
-
-  /// A future that completes when the browser exits.
-  ///
-  /// If there's a problem starting or running the browser, this will complete
-  /// with an error.
-  Future get onExit => _onExitCompleter.future;
-  final _onExitCompleter = Completer();
-
-  /// Standard IO streams for the underlying browser process.
-  final _ioSubscriptions = <StreamSubscription>[];
-
-  /// Creates a new browser.
-  ///
-  /// This is intended to be called by subclasses. They pass in [startBrowser],
-  /// which asynchronously returns the browser process. Any errors in
-  /// [startBrowser] (even those raised asynchronously after it returns) are
-  /// piped to [onExit] and will cause the browser to be killed.
-  Browser(Future<Process> startBrowser()) {
-    // Don't return a Future here because there's no need for the caller to wait
-    // for the process to actually start. They should just wait for the HTTP
-    // request instead.
-    runZoned(() async {
-      var process = await startBrowser();
-      _processCompleter.complete(process);
-
-      var output = Uint8Buffer();
-      drainOutput(Stream<List<int>> stream) {
-        try {
-          _ioSubscriptions
-              .add(stream.listen(output.addAll, cancelOnError: true));
-        } on StateError catch (_) {}
-      }
-
-      // If we don't drain the stdout and stderr the process can hang.
-      drainOutput(process.stdout);
-      drainOutput(process.stderr);
-
-      var exitCode = await process.exitCode;
-
-      // This hack dodges an otherwise intractable race condition. When the user
-      // presses Control-C, the signal is sent to the browser and the test
-      // runner at the same time. It's possible for the browser to exit before
-      // the [Browser.close] is called, which would trigger the error below.
-      //
-      // A negative exit code signals that the process exited due to a signal.
-      // However, it's possible that this signal didn't come from the user's
-      // Control-C, in which case we do want to throw the error. The only way to
-      // resolve the ambiguity is to wait a brief amount of time and see if this
-      // browser is actually closed.
-      if (!_closed && exitCode < 0) {
-        await Future.delayed(Duration(milliseconds: 200));
-      }
-
-      if (!_closed && exitCode != 0) {
-        var outputString = utf8.decode(output);
-        var message = '$name failed with exit code $exitCode.';
-        if (outputString.isNotEmpty) {
-          message += '\nStandard output:\n$outputString';
-        }
-
-        throw Exception(message);
-      }
-
-      _onExitCompleter.complete();
-    }, onError: (error, StackTrace stackTrace) {
-      // Ignore any errors after the browser has been closed.
-      if (_closed) return;
-
-      // Make sure the process dies even if the error wasn't fatal.
-      _process.then((process) => process.kill());
-
-      if (stackTrace == null) stackTrace = Trace.current();
-      if (_onExitCompleter.isCompleted) return;
-      _onExitCompleter.completeError(
-          Exception('Failed to run $name: ${getErrorMessage(error)}.'),
-          stackTrace);
-    });
-  }
-
-  /// Kills the browser process.
-  ///
-  /// Returns the same [Future] as [onExit], except that it won't emit
-  /// exceptions.
-  Future close() async {
-    _closed = true;
-
-    // If we don't manually close the stream the test runner can hang.
-    // For example this happens with Chrome Headless.
-    // See SDK issue: https://github.com/dart-lang/sdk/issues/31264
-    for (var stream in _ioSubscriptions) {
-      unawaited(stream.cancel());
-    }
-
-    (await _process).kill();
-
-    // Swallow exceptions. The user should explicitly use [onExit] for these.
-    return onExit.catchError((_) {});
-  }
-}
-
-/// A class for running an instance of Chrome.
-///
-/// Most of the communication with the browser is expected to happen via HTTP,
-/// so this exposes a bare-bones API. The browser starts as soon as the class is
-/// constructed, and is killed when [close] is called.
-///
-/// Any errors starting or running the process are reported through [onExit].
-class Chrome extends Browser {
-  @override
-  final name = 'Chrome';
-
-  @override
-  final Future<Uri> remoteDebuggerUrl;
-
-  static String version;
-
-  /// Starts a new instance of Chrome open to the given [url], which may be a
-  /// [Uri] or a [String].
-  factory Chrome(Uri url, {bool debug = false}) {
-    assert(version != null);
-    var remoteDebuggerCompleter = Completer<Uri>.sync();
-    return Chrome._(() async {
-      final BrowserInstallation installation = await getOrInstallChrome(
-        version,
-        infoLog: isCirrus ? stdout : _DevNull(),
-      );
-
-      // A good source of various Chrome CLI options:
-      // https://peter.sh/experiments/chromium-command-line-switches/
-      //
-      // Things to try:
-      // --font-render-hinting
-      // --enable-font-antialiasing
-      // --gpu-rasterization-msaa-sample-count
-      // --disable-gpu
-      // --disallow-non-exact-resource-reuse
-      // --disable-font-subpixel-positioning
-      final bool isChromeNoSandbox = Platform.environment['CHROME_NO_SANDBOX'] == 'true';
-      var dir = createTempDir();
-      var args = [
-        '--user-data-dir=$dir',
-        url.toString(),
-        if (!debug) '--headless',
-        if (isChromeNoSandbox) '--no-sandbox',
-        '--window-size=$_kMaxScreenshotWidth,$_kMaxScreenshotHeight', // When headless, this is the actual size of the viewport
-        '--disable-extensions',
-        '--disable-popup-blocking',
-        '--bwsi',
-        '--no-first-run',
-        '--no-default-browser-check',
-        '--disable-default-apps',
-        '--disable-translate',
-        '--remote-debugging-port=$_kChromeDevtoolsPort',
-      ];
-
-      final Process process = await Process.start(installation.executable, args);
-
-      remoteDebuggerCompleter.complete(getRemoteDebuggerUrl(
-          Uri.parse('http://localhost:$_kChromeDevtoolsPort')));
-
-      unawaited(process.exitCode
-          .then((_) => Directory(dir).deleteSync(recursive: true)));
-
-      return process;
-    }, remoteDebuggerCompleter.future);
-  }
-
-  Chrome._(Future<Process> startBrowser(), this.remoteDebuggerUrl)
-      : super(startBrowser);
-}
-
-/// A string sink that swallows all input.
-class _DevNull implements StringSink {
-  @override
-  void write(Object obj) {
-  }
-
-  @override
-  void writeAll(Iterable objects, [String separator = ""]) {
-  }
-
-  @override
-  void writeCharCode(int charCode) {
-  }
-
-  @override
-  void writeln([Object obj = ""]) {
-  }
-}
-
 bool get isCirrus => Platform.environment['CIRRUS_CI'] == 'true';
diff --git a/lib/web_ui/dev/test_runner.dart b/lib/web_ui/dev/test_runner.dart
index a2a1851407b6a..842b4e4e7adfd 100644
--- a/lib/web_ui/dev/test_runner.dart
+++ b/lib/web_ui/dev/test_runner.dart
@@ -14,6 +14,7 @@ import 'package:test_api/src/backend/runtime.dart'; // ignore: implementation_im
 import 'package:test_core/src/executable.dart'
     as test; // ignore: implementation_imports
 
+import 'chrome.dart';
 import 'chrome_installer.dart';
 import 'test_platform.dart';
 import 'environment.dart';

From fb430770f39e52599a1ff82537cd13ea5e706346 Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Mon, 21 Oct 2019 15:57:34 -0700
Subject: [PATCH 2/9] remove download.dart. Not complete for now

---
 lib/web_ui/dev/download.dart | 28 ----------------------------
 lib/web_ui/dev/felt.dart     |  4 +---
 2 files changed, 1 insertion(+), 31 deletions(-)
 delete mode 100644 lib/web_ui/dev/download.dart

diff --git a/lib/web_ui/dev/download.dart b/lib/web_ui/dev/download.dart
deleted file mode 100644
index 57f708177f896..0000000000000
--- a/lib/web_ui/dev/download.dart
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2013 The Flutter 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 'dart:async';
-
-import 'package:args/command_runner.dart';
-
-import 'common.dart';
-import 'firefox_installer.dart';
-
-class DownloadCommand extends Command<bool> {
-  DownloadCommand();
-
-  @override
-  String get name => 'download';
-
-  @override
-  String get description => 'Deletes build caches and artifacts.';
-
-  @override
-  FutureOr<bool> run() async {
-    BrowserInstallation installation = await getOrInstallFirefox('69.0.2');
-
-    print('Firefox installed: ${installation.version}');
-    print('Firefox installed: ${installation.executable}');
-  }
-}
diff --git a/lib/web_ui/dev/felt.dart b/lib/web_ui/dev/felt.dart
index 172d9444916e8..1830c051b9ef6 100644
--- a/lib/web_ui/dev/felt.dart
+++ b/lib/web_ui/dev/felt.dart
@@ -8,7 +8,6 @@ import 'package:args/command_runner.dart';
 
 import 'build.dart';
 import 'clean.dart';
-import 'download.dart';
 import 'licenses.dart';
 import 'test_runner.dart';
 
@@ -19,8 +18,7 @@ CommandRunner runner = CommandRunner<bool>(
   ..addCommand(CleanCommand())
   ..addCommand(LicensesCommand())
   ..addCommand(TestCommand())
-  ..addCommand(BuildCommand())
-  ..addCommand(DownloadCommand());
+  ..addCommand(BuildCommand());
 
 void main(List<String> args) async {
   if (args.isEmpty) {

From 54d3267f0f127e7faeefca9ff60c6d6afdd23014 Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Mon, 21 Oct 2019 16:23:06 -0700
Subject: [PATCH 3/9] uncomment firefox.dart. Adding new CL parameters.

---
 lib/web_ui/dev/firefox.dart | 123 ++++++++++++++++--------------------
 1 file changed, 54 insertions(+), 69 deletions(-)

diff --git a/lib/web_ui/dev/firefox.dart b/lib/web_ui/dev/firefox.dart
index d63d9a524ca81..ed817485f09ac 100644
--- a/lib/web_ui/dev/firefox.dart
+++ b/lib/web_ui/dev/firefox.dart
@@ -1,82 +1,67 @@
+import 'dart:async';
+import 'dart:io';
 
-// import 'dart:async';
-// import 'dart:io';
+import 'package:pedantic/pedantic.dart';
 
-// import 'package:pedantic/pedantic.dart';
+import 'package:test_core/src/util/io.dart'; // ignore: implementation_imports
 
-// import 'package:test_core/src/util/io.dart'; // ignore: implementation_imports
+import 'browser.dart';
+import 'firefox_installer.dart';
+import 'common.dart';
 
-// import 'browser.dart';
-// import 'firefox_installer.dart';
-// import 'common.dart';
+/// A class for running an instance of Firefox.
+///
+/// Most of the communication with the browser is expected to happen via HTTP,
+/// so this exposes a bare-bones API. The browser starts as soon as the class is
+/// constructed, and is killed when [close] is called.
+///
+/// Any errors starting or running the process are reported through [onExit].
+class Firefox extends Browser {
+  @override
+  final name = 'Firefox';
 
-// /// A class for running an instance of Firefox.
-// ///
-// /// Most of the communication with the browser is expected to happen via HTTP,
-// /// so this exposes a bare-bones API. The browser starts as soon as the class is
-// /// constructed, and is killed when [close] is called.
-// ///
-// /// Any errors starting or running the process are reported through [onExit].
-// class Firefox extends Browser {
-//   @override
-//   final name = 'Firefox';
+  @override
+  final Future<Uri> remoteDebuggerUrl;
 
-//   @override
-//   final Future<Uri> remoteDebuggerUrl;
+  static String version;
 
-//   static String version;
+  /// Starts a new instance of Firefox open to the given [url], which may be a
+  /// [Uri] or a [String].
+  factory Firefox(Uri url, {bool debug = false}) {
+    assert(version != null);
+    var remoteDebuggerCompleter = Completer<Uri>.sync();
+    return Firefox._(() async {
+      final BrowserInstallation installation = await getOrInstallFirefox(
+        version,
+        infoLog: isCirrus ? stdout : DevNull(),
+      );
 
-//   /// Starts a new instance of Firefox open to the given [url], which may be a
-//   /// [Uri] or a [String].
-//   factory Firefox(Uri url, {bool debug = false}) {
-//     assert(version != null);
-//     var remoteDebuggerCompleter = Completer<Uri>.sync();
-//     return Firefox._(() async {
-//       final BrowserInstallation installation = await getOrInstallFirefox(
-//         version,
-//         infoLog: isCirrus ? stdout : DevNull(),
-//       );
+      // A good source of various Firefox Command Line options:
+      // https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options#Browser
+      //
+      var dir = createTempDir();
+      var args = [
+        url.toString(),
+        if (!debug) '--headless',
+        '-width $kMaxScreenshotWidth'
+        '-height $kMaxScreenshotHeight',
+        '-new-window',
+        '-new-instance',
+        '--start-debugger-server $kDevtoolsPort',
+      ];
 
-//       // A good source of various Firefox CLI options:
-//       // https://peter.sh/experiments/chromium-command-line-switches/
-//       //
-//       // Things to try:
-//       // --font-render-hinting
-//       // --enable-font-antialiasing
-//       // --gpu-rasterization-msaa-sample-count
-//       // --disable-gpu
-//       // --disallow-non-exact-resource-reuse
-//       // --disable-font-subpixel-positioning
-//       final bool isFirefoxNoSandbox = Platform.environment['CHROME_NO_SANDBOX'] == 'true';
-//       var dir = createTempDir();
-//       var args = [
-//         '--user-data-dir=$dir',
-//         url.toString(),
-//         if (!debug) '--headless',
-//         if (isFirefoxNoSandbox) '--no-sandbox',
-//         '--window-size=$kMaxScreenshotWidth,$kMaxScreenshotHeight', // When headless, this is the actual size of the viewport
-//         '--disable-extensions',
-//         '--disable-popup-blocking',
-//         '--bwsi',
-//         '--no-first-run',
-//         '--no-default-browser-check',
-//         '--disable-default-apps',
-//         '--disable-translate',
-//         '--remote-debugging-port=$kDevtoolsPort',
-//       ];
+      final Process process = await Process.start(installation.executable, args);
 
-//       final Process process = await Process.start(installation.executable, args);
+      remoteDebuggerCompleter.complete(getRemoteDebuggerUrl(
+          Uri.parse('http://localhost:$kDevtoolsPort')));
 
-//       remoteDebuggerCompleter.complete(getRemoteDebuggerUrl(
-//           Uri.parse('http://localhost:$_kFirefoxDevtoolsPort')));
+      unawaited(process.exitCode
+          .then((_) => Directory(dir).deleteSync(recursive: true)));
 
-//       unawaited(process.exitCode
-//           .then((_) => Directory(dir).deleteSync(recursive: true)));
+      return process;
+    }, remoteDebuggerCompleter.future);
+  }
 
-//       return process;
-//     }, remoteDebuggerCompleter.future);
-//   }
-
-//   Firefox._(Future<Process> startBrowser(), this.remoteDebuggerUrl)
-//       : super(startBrowser);
-// }
+  Firefox._(Future<Process> startBrowser(), this.remoteDebuggerUrl)
+      : super(startBrowser);
+}

From 04dd97d9b4095a089e7b62dcc53bc6df2f75f104 Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Tue, 22 Oct 2019 12:48:44 -0700
Subject: [PATCH 4/9] Licence headers added.

---
 lib/web_ui/dev/browser.dart | 4 ++++
 lib/web_ui/dev/chrome.dart  | 3 +++
 lib/web_ui/dev/firefox.dart | 4 ++++
 3 files changed, 11 insertions(+)

diff --git a/lib/web_ui/dev/browser.dart b/lib/web_ui/dev/browser.dart
index 852ec335f9134..8301289acf541 100644
--- a/lib/web_ui/dev/browser.dart
+++ b/lib/web_ui/dev/browser.dart
@@ -1,3 +1,7 @@
+// Copyright 2013 The Flutter 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 'dart:async';
 import 'dart:convert';
 import 'dart:io';
diff --git a/lib/web_ui/dev/chrome.dart b/lib/web_ui/dev/chrome.dart
index 6f895833ff948..f2d1e3a6e9b63 100644
--- a/lib/web_ui/dev/chrome.dart
+++ b/lib/web_ui/dev/chrome.dart
@@ -1,3 +1,6 @@
+// Copyright 2013 The Flutter 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 'dart:async';
 import 'dart:io';
diff --git a/lib/web_ui/dev/firefox.dart b/lib/web_ui/dev/firefox.dart
index ed817485f09ac..e1a43301eb128 100644
--- a/lib/web_ui/dev/firefox.dart
+++ b/lib/web_ui/dev/firefox.dart
@@ -1,3 +1,7 @@
+// Copyright 2013 The Flutter 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 'dart:async';
 import 'dart:io';
 

From 92489dbe4df7f8e3c93851d744d4b3487a1a509f Mon Sep 17 00:00:00 2001
From: nturgut <nurhan@google.com>
Date: Tue, 22 Oct 2019 16:32:22 -0700
Subject: [PATCH 5/9] adding more comments to firefox_installer

---
 lib/web_ui/dev/firefox_installer.dart | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/web_ui/dev/firefox_installer.dart b/lib/web_ui/dev/firefox_installer.dart
index 14c6bcc4a145e..fda7b5b11b655 100644
--- a/lib/web_ui/dev/firefox_installer.dart
+++ b/lib/web_ui/dev/firefox_installer.dart
@@ -27,7 +27,8 @@ Future<BrowserInstallation> getOrInstallFirefox(
   StringSink infoLog,
 }) async {
 
-  // Installation support is implemented only for Linux for now.
+  // These tests are aimed to run only on the Linux containers in Cirrus.
+  // Therefore Firefox installation is implemented only for Linux now.
   if(!io.Platform.isLinux) {
     throw UnimplementedError();
   }

From a9f7e33d57f57ad84b8d7a829598e069d97fb7db Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Wed, 23 Oct 2019 10:29:09 -0700
Subject: [PATCH 6/9] adding test for firefox download

---
 .cirrus.yml                                | 12 +++++
 lib/web_ui/dev/firefox_installer.dart      |  3 +-
 lib/web_ui/dev/firefox_installer_test.dart | 60 ++++++++++++++++++++++
 3 files changed, 73 insertions(+), 2 deletions(-)
 create mode 100644 lib/web_ui/dev/firefox_installer_test.dart

diff --git a/.cirrus.yml b/.cirrus.yml
index 9a091276ebe63..a463d9219850a 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -63,6 +63,18 @@ task:
       test_framework_script: |
         cd $FRAMEWORK_PATH/flutter/packages/flutter
         ../../bin/flutter test --local-engine=host_debug_unopt
+    - name: build_and_test_web_linux_firefox
+      compile_host_script: |
+        cd $ENGINE_PATH/src
+        ./flutter/tools/gn --unoptimized --full-dart-sdk
+        ninja -C out/host_debug_unopt
+      test_web_engine_firefox_script: |
+        cd $ENGINE_PATH/src/flutter/web_sdk/web_engine_tester
+        $ENGINE_PATH/src/out/host_debug_unopt/dart-sdk/bin/pub get
+        cd $ENGINE_PATH/src/flutter/lib/web_ui
+        $ENGINE_PATH/src/out/host_debug_unopt/dart-sdk/bin/pub get
+        export DART="$ENGINE_PATH/src/out/host_debug_unopt/dart-sdk/bin/dart"
+        $DART lib/web_ui/dev/firefox_installer_test.dart
     - name: build_and_test_android_unopt_debug
       env:
         USE_ANDROID: "True"
diff --git a/lib/web_ui/dev/firefox_installer.dart b/lib/web_ui/dev/firefox_installer.dart
index fda7b5b11b655..641b9ad638591 100644
--- a/lib/web_ui/dev/firefox_installer.dart
+++ b/lib/web_ui/dev/firefox_installer.dart
@@ -26,10 +26,9 @@ Future<BrowserInstallation> getOrInstallFirefox(
   String requestedVersion, {
   StringSink infoLog,
 }) async {
-
   // These tests are aimed to run only on the Linux containers in Cirrus.
   // Therefore Firefox installation is implemented only for Linux now.
-  if(!io.Platform.isLinux) {
+  if (!io.Platform.isLinux) {
     throw UnimplementedError();
   }
 
diff --git a/lib/web_ui/dev/firefox_installer_test.dart b/lib/web_ui/dev/firefox_installer_test.dart
new file mode 100644
index 0000000000000..613cd51b1e7d0
--- /dev/null
+++ b/lib/web_ui/dev/firefox_installer_test.dart
@@ -0,0 +1,60 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+@TestOn('vm')
+
+import 'dart:io' as io;
+
+import 'package:path/path.dart' as path;
+import 'package:test/test.dart';
+
+import 'common.dart';
+import 'environment.dart';
+import 'firefox_installer.dart';
+
+void main() async {
+  void deleteFirefoxInstallIfExists() {
+    final io.Directory firefoxInstallationDir = io.Directory(
+      path.join(environment.webUiDartToolDir.path, 'firefox'),
+    );
+
+    if (firefoxInstallationDir.existsSync()) {
+      firefoxInstallationDir.deleteSync(recursive: true);
+    }
+  }
+
+  setUpAll(() {
+    deleteFirefoxInstallIfExists();
+  });
+
+  tearDown(() {
+    deleteFirefoxInstallIfExists();
+  });
+
+  test('installs a given version of Firefox', () async {
+    FirefoxInstaller installer = FirefoxInstaller(version: '69.0.2');
+    expect(installer.isInstalled, isFalse);
+
+    BrowserInstallation installation = await getOrInstallFirefox('69.0.2');
+
+    expect(installation.version, '69.0.2');
+    expect(installer.isInstalled, isTrue);
+  });
+
+  test('can find the system version when a firefox is already installed',
+      () async {
+    final logSink = StringBuffer();
+    await getOrInstallFirefox('69.0.2', infoLog: logSink);
+    expect(logSink.length, greaterThanOrEqualTo(1));
+
+    final logSinkForInstallation = StringBuffer();
+    expect(logSinkForInstallation.isEmpty, isTrue);
+    await getOrInstallFirefox('system', infoLog: logSinkForInstallation);
+
+    print(logSinkForInstallation.toString());
+
+    // There are no logs on installation since the system version is used.
+    expect(logSinkForInstallation.isEmpty, isTrue);
+  });
+}

From d4b31a1048daaf96204fce7a44399e9e5d18e23b Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Wed, 23 Oct 2019 10:54:37 -0700
Subject: [PATCH 7/9] address pr comments. change directory for test in
 .cirrus.yml

---
 lib/web_ui/dev/firefox_installer_test.dart | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/web_ui/dev/firefox_installer_test.dart b/lib/web_ui/dev/firefox_installer_test.dart
index 613cd51b1e7d0..0e265c369a787 100644
--- a/lib/web_ui/dev/firefox_installer_test.dart
+++ b/lib/web_ui/dev/firefox_installer_test.dart
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-@TestOn('vm')
+@TestOn('vm && linux')
 
 import 'dart:io' as io;
 
@@ -40,12 +40,15 @@ void main() async {
 
     expect(installation.version, '69.0.2');
     expect(installer.isInstalled, isTrue);
+    expect(io.File(installation.executable).existsSync(), isTrue);
   });
 
   test('can find the system version when a firefox is already installed',
       () async {
     final logSink = StringBuffer();
-    await getOrInstallFirefox('69.0.2', infoLog: logSink);
+    BrowserInstallation installation =
+        await getOrInstallFirefox('69.0.2', infoLog: logSink);
+    expect(io.File(installation.executable).existsSync(), isTrue);
     expect(logSink.length, greaterThanOrEqualTo(1));
 
     final logSinkForInstallation = StringBuffer();

From 9b4222b36998c7c431713dcbd23b650fae77da8f Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Wed, 23 Oct 2019 10:57:23 -0700
Subject: [PATCH 8/9] change directory for test_web_engine_firefox_script

---
 .cirrus.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.cirrus.yml b/.cirrus.yml
index a463d9219850a..1f9e1e6b505ee 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -74,7 +74,7 @@ task:
         cd $ENGINE_PATH/src/flutter/lib/web_ui
         $ENGINE_PATH/src/out/host_debug_unopt/dart-sdk/bin/pub get
         export DART="$ENGINE_PATH/src/out/host_debug_unopt/dart-sdk/bin/dart"
-        $DART lib/web_ui/dev/firefox_installer_test.dart
+        $DART dev/firefox_installer_test.dart
     - name: build_and_test_android_unopt_debug
       env:
         USE_ANDROID: "True"

From 13deaf4e24c5c32e76cebf12181b9c5bb2f09f9b Mon Sep 17 00:00:00 2001
From: Nurhan Turgut <nurhan@google.com>
Date: Wed, 23 Oct 2019 12:43:09 -0700
Subject: [PATCH 9/9] removing the system test.

---
 lib/web_ui/dev/firefox_installer_test.dart | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/lib/web_ui/dev/firefox_installer_test.dart b/lib/web_ui/dev/firefox_installer_test.dart
index 0e265c369a787..0d6c73e6b129a 100644
--- a/lib/web_ui/dev/firefox_installer_test.dart
+++ b/lib/web_ui/dev/firefox_installer_test.dart
@@ -42,22 +42,4 @@ void main() async {
     expect(installer.isInstalled, isTrue);
     expect(io.File(installation.executable).existsSync(), isTrue);
   });
-
-  test('can find the system version when a firefox is already installed',
-      () async {
-    final logSink = StringBuffer();
-    BrowserInstallation installation =
-        await getOrInstallFirefox('69.0.2', infoLog: logSink);
-    expect(io.File(installation.executable).existsSync(), isTrue);
-    expect(logSink.length, greaterThanOrEqualTo(1));
-
-    final logSinkForInstallation = StringBuffer();
-    expect(logSinkForInstallation.isEmpty, isTrue);
-    await getOrInstallFirefox('system', infoLog: logSinkForInstallation);
-
-    print(logSinkForInstallation.toString());
-
-    // There are no logs on installation since the system version is used.
-    expect(logSinkForInstallation.isEmpty, isTrue);
-  });
 }