From cd83fb33bcf2a918f12443d45ee8a5bdd6b6808c Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Mon, 15 Nov 2021 15:33:26 -0800
Subject: [PATCH 01/17] Add embedder API for replacing the default asset
 manager

---
 shell/platform/embedder/embedder.h | 55 ++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index e8b769ef4cbef..b0c0a2e7f5d6d 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1345,12 +1345,62 @@ typedef void (*FlutterLogMessageCallback)(const char* /* tag */,
 /// FlutterEngine instance in AOT mode.
 typedef struct _FlutterEngineAOTData* FlutterEngineAOTData;
 
+/// An immutable buffer of potentially shared data. 
+typedef struct {
+  /// The size of the struct. Must be sizeof(FlutterEngineMapping).
+  size_t struct_size;
+
+  /// A pointer to the data accessed by the Flutter Engine. The data will not be
+  /// mutated by the Flutter Engine, and must not be mutated by the Embedder until
+  /// the mapping is destroyed.
+  const uint8_t* data;
+  /// The size of the data backed by this mapping. The data must be valid for
+  /// reading until this point. Bytes past the end are undefined and not accessed
+  /// by the Engine. 
+  size_t data_size;
+
+  /// An opaque baton passed back to the embedder when the destruction_callback is
+  /// invoked. The engine does not interpret this field in any way.
+  void* user_data;
+  /// Called once by the engine to destroy this mapping. The `user_data` specified
+  /// above is passed in as the only argument. This call may mutate/free/unmap the
+  /// data, as it will no longer be accessed by the Flutter Engine.
+  VoidCallback destruction_callback;
+} FlutterEngineMapping;
+
+/// Callback for fetching assets for a `FlutterEngineAssetResolver`.
+///
+/// This may be called by multiple threads.
+///
+/// The `asset_name` parameter contains the path to the asset to load.
+/// `user_data` is the user data from `FlutterEngineAssetResolver`, registered via
+/// `FlutterProjectArgs`.
+///
+/// If the asset was found and successfully loaded, return a valid
+/// `FlutterEngineMapping`. Otherwise return NULL to indicate an error occurred 
+/// while loading the asset.
+typedef FlutterEngineMapping* (*FlutterAssetResolverGetAssetCallback)(const char* /* asset_name */,
+                                                                      void* /* user_data */);
+
+/// Resolves assets on the behalf of the Flutter Engine, instead of accessing the
+/// filesystem directly.
+typedef struct {
+  /// The size of the struct. Must be sizeof(FlutterEngineAssetResolver).
+  size_t struct_size;
+
+  /// Required. Gets and returns an asset if available. See the documentation on
+  /// `FlutterAssetResolverGetAssetCallback` for more information.
+  FlutterAssetResolverGetAssetCallback get_asset;
+} FlutterEngineAssetResolver;
+
 typedef struct {
   /// The size of this struct. Must be sizeof(FlutterProjectArgs).
   size_t struct_size;
   /// The path to the Flutter assets directory containing project assets. The
   /// string can be collected after the call to `FlutterEngineRun` returns. The
   /// string must be NULL terminated.
+  ///
+  /// If `asset_resolver` is provided, this path is ignored and may be NULL.
   const char* assets_path;
   /// The path to the Dart file containing the `main` entry point.
   /// The string can be collected after the call to `FlutterEngineRun` returns.
@@ -1589,6 +1639,11 @@ typedef struct {
   //
   // The first argument is the `user_data` from `FlutterEngineInitialize`.
   OnPreEngineRestartCallback on_pre_engine_restart_callback;
+
+  /// An asset resolver that fetches assets for the Engine.
+  ///
+  /// If provided, this replaces the default asset resolver.
+  const FlutterEngineAssetResolver* asset_resolver;
 } FlutterProjectArgs;
 
 #ifndef FLUTTER_ENGINE_NO_PROTOTYPES

From 910bb88c42656978e1637c7ba263f51148c1eb47 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Mon, 15 Nov 2021 15:49:09 -0800
Subject: [PATCH 02/17] Add EmbedderMapping

---
 shell/platform/embedder/BUILD.gn            |  2 +
 shell/platform/embedder/embedder_mapping.cc | 58 +++++++++++++++++++++
 shell/platform/embedder/embedder_mapping.h  | 17 ++++++
 3 files changed, 77 insertions(+)
 create mode 100644 shell/platform/embedder/embedder_mapping.cc
 create mode 100644 shell/platform/embedder/embedder_mapping.h

diff --git a/shell/platform/embedder/BUILD.gn b/shell/platform/embedder/BUILD.gn
index 529f48a7ebd41..b07e1bfa387b4 100644
--- a/shell/platform/embedder/BUILD.gn
+++ b/shell/platform/embedder/BUILD.gn
@@ -44,6 +44,8 @@ template("embedder_source_set") {
       "embedder_include2.c",
       "embedder_layers.cc",
       "embedder_layers.h",
+      "embedder_mapping.cc",
+      "embedder_mapping.h",
       "embedder_platform_message_response.cc",
       "embedder_platform_message_response.h",
       "embedder_render_target.cc",
diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
new file mode 100644
index 0000000000000..6588a7369f42e
--- /dev/null
+++ b/shell/platform/embedder/embedder_mapping.cc
@@ -0,0 +1,58 @@
+// 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.
+
+#include "flutter/shell/platform/embedder/embedder_mapping.h"
+#include "flutter/shell/platform/embedder/embedder_struct_macros.h"
+
+namespace flutter {
+
+class EmbedderMapping final : public fml::Mapping {
+  public:
+  EmbedderMapping(const uint8_t* data,
+                  size_t size,
+                  void* user_data,
+                  VoidCallback destruction_callback)
+      : data_(data),
+        size_(size),
+        user_data_(user_data),
+        destruction_callback_(destruction_callback) {}
+  
+  ~EmbedderMapping() override {
+    if (destruction_callback_) destruction_callback_(user_data_);
+  }
+
+  // |Mapping|
+  size_t GetSize() const override {
+    return size_;
+  }
+
+  // |Mapping|
+  const uint8_t* GetMapping() const override {
+    return data_;
+  }
+
+  // |Mapping|
+  bool IsDontNeedSafe() const override {
+    return false;
+  }
+
+private:
+  const uint8_t* data_;
+  size_t size_;
+  void* user_data_;
+  VoidCallback destruction_callback_;
+  
+  FML_DISALLOW_COPY_AND_ASSIGN(EmbedderMapping);
+};
+
+std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMapping* mapping) {
+  return std::make_unique<EmbedderMapping>(
+    SAFE_ACCESS(mapping, data, nullptr),
+    SAFE_ACCESS(mapping, data_size, 0),
+    SAFE_ACCESS(mapping, user_data, nullptr),
+    SAFE_ACCESS(mapping, destruction_callback, nullptr)
+  );
+}
+
+}  // namespace flutter
diff --git a/shell/platform/embedder/embedder_mapping.h b/shell/platform/embedder/embedder_mapping.h
new file mode 100644
index 0000000000000..85658a3aaa51e
--- /dev/null
+++ b/shell/platform/embedder/embedder_mapping.h
@@ -0,0 +1,17 @@
+// 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.
+
+#ifndef FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_MAPPING_H_
+#define FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_MAPPING_H_
+
+#include "flutter/fml/mapping.h"
+#include "flutter/shell/platform/embedder/embedder.h"
+
+namespace flutter {
+
+std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMapping* mapping);
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_MAPPING_H_

From d5eef2b011f510d70b7b89e2e3104b80c1884434 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Tue, 16 Nov 2021 13:52:40 -0800
Subject: [PATCH 03/17] Create mappings instead of returning info struct

---
 shell/platform/embedder/embedder.cc         | 15 ++++++++++++
 shell/platform/embedder/embedder.h          | 27 +++++++++++++++++++--
 shell/platform/embedder/embedder_mapping.cc |  4 +--
 shell/platform/embedder/embedder_mapping.h  |  2 +-
 4 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index f8496ffc0b0a9..be951f030fb34 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -49,6 +49,7 @@ extern const intptr_t kPlatformStrongDillSize;
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/embedder/embedder_engine.h"
 #include "flutter/shell/platform/embedder/embedder_external_texture_resolver.h"
+#include "flutter/shell/platform/embedder/embedder_mapping.h"
 #include "flutter/shell/platform/embedder/embedder_platform_message_response.h"
 #include "flutter/shell/platform/embedder/embedder_render_target.h"
 #include "flutter/shell/platform/embedder/embedder_struct_macros.h"
@@ -2360,6 +2361,19 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
   }
 }
 
+FlutterEngineResult FlutterEngineCreateMapping(
+    const FlutterEngineMappingCreateInfo* create_info,
+    FlutterEngineMapping* out_mapping) {
+  if (SAFE_ACCESS(create_info, data, nullptr) == nullptr && SAFE_ACCESS(create_info, data_size, 0) > 0) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments, "Invalid mapping specified.");
+  }
+
+  auto mapping = flutter::CreateEmbedderMapping(create_info);
+  *out_mapping = reinterpret_cast<FlutterEngineMapping>(mapping.release());
+
+  return kSuccess;
+}
+
 FlutterEngineResult FlutterEngineGetProcAddresses(
     FlutterEngineProcTable* table) {
   if (!table) {
@@ -2410,6 +2424,7 @@ FlutterEngineResult FlutterEngineGetProcAddresses(
   SET_PROC(PostCallbackOnAllNativeThreads,
            FlutterEnginePostCallbackOnAllNativeThreads);
   SET_PROC(NotifyDisplayUpdate, FlutterEngineNotifyDisplayUpdate);
+  SET_PROC(CreateMapping, FlutterEngineCreateMapping);
 #undef SET_PROC
 
   return kSuccess;
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index b0c0a2e7f5d6d..22048c4eab516 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1366,7 +1366,9 @@ typedef struct {
   /// above is passed in as the only argument. This call may mutate/free/unmap the
   /// data, as it will no longer be accessed by the Flutter Engine.
   VoidCallback destruction_callback;
-} FlutterEngineMapping;
+} FlutterEngineMappingCreateInfo;
+
+typedef struct FlutterEngineMappingPrivate* FlutterEngineMapping;
 
 /// Callback for fetching assets for a `FlutterEngineAssetResolver`.
 ///
@@ -1379,7 +1381,7 @@ typedef struct {
 /// If the asset was found and successfully loaded, return a valid
 /// `FlutterEngineMapping`. Otherwise return NULL to indicate an error occurred 
 /// while loading the asset.
-typedef FlutterEngineMapping* (*FlutterAssetResolverGetAssetCallback)(const char* /* asset_name */,
+typedef FlutterEngineMapping (*FlutterAssetResolverGetAssetCallback)(const char* /* asset_name */,
                                                                       void* /* user_data */);
 
 /// Resolves assets on the behalf of the Flutter Engine, instead of accessing the
@@ -2306,6 +2308,23 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
     const FlutterEngineDisplay* displays,
     size_t display_count);
 
+//------------------------------------------------------------------------------
+/// @brief      Creates a `FlutterEngineMapping` using the given creation info.
+///             The backing memory is never mutated by the Engine, and must not
+///             be mutated by the embedder until the mapping is destroyed.
+///             The engine may access the mapping from multiple threads, and may
+///             destroy the mapping from any thread.
+///
+/// @param[in]  create_info     Struct describing the mapping to create.
+/// @param[out] out_mapping     The created mapping, if successful.
+///
+/// @return     Whether the mapping was successfully created.
+///
+FLUTTER_EXPORT
+FlutterEngineResult FlutterEngineCreateMapping(
+    const FlutterEngineMappingCreateInfo* create_info,
+    FlutterEngineMapping* out_mapping);
+
 #endif  // !FLUTTER_ENGINE_NO_PROTOTYPES
 
 // Typedefs for the function pointers in FlutterEngineProcTable.
@@ -2422,6 +2441,9 @@ typedef FlutterEngineResult (*FlutterEngineNotifyDisplayUpdateFnPtr)(
     FlutterEngineDisplaysUpdateType update_type,
     const FlutterEngineDisplay* displays,
     size_t display_count);
+typedef FlutterEngineResult (*FlutterEngineCreateMappingFnPtr)(
+    const FlutterEngineMappingCreateInfo* create_info,
+    FlutterEngineMapping* out_mapping);
 
 /// Function-pointer-based versions of the APIs above.
 typedef struct {
@@ -2466,6 +2488,7 @@ typedef struct {
   FlutterEnginePostCallbackOnAllNativeThreadsFnPtr
       PostCallbackOnAllNativeThreads;
   FlutterEngineNotifyDisplayUpdateFnPtr NotifyDisplayUpdate;
+  FlutterEngineCreateMappingFnPtr CreateMapping;
 } FlutterEngineProcTable;
 
 //------------------------------------------------------------------------------
diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
index 6588a7369f42e..55917ff94cd34 100644
--- a/shell/platform/embedder/embedder_mapping.cc
+++ b/shell/platform/embedder/embedder_mapping.cc
@@ -42,11 +42,11 @@ class EmbedderMapping final : public fml::Mapping {
   size_t size_;
   void* user_data_;
   VoidCallback destruction_callback_;
-  
+
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderMapping);
 };
 
-std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMapping* mapping) {
+std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMappingCreateInfo* mapping) {
   return std::make_unique<EmbedderMapping>(
     SAFE_ACCESS(mapping, data, nullptr),
     SAFE_ACCESS(mapping, data_size, 0),
diff --git a/shell/platform/embedder/embedder_mapping.h b/shell/platform/embedder/embedder_mapping.h
index 85658a3aaa51e..2315939af6e77 100644
--- a/shell/platform/embedder/embedder_mapping.h
+++ b/shell/platform/embedder/embedder_mapping.h
@@ -10,7 +10,7 @@
 
 namespace flutter {
 
-std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMapping* mapping);
+std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMappingCreateInfo* mapping);
 
 }  // namespace flutter
 

From 7719dcf7bb523757c379e41a7e2b0b82ef02d229 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 17 Nov 2021 14:32:00 -0800
Subject: [PATCH 04/17] Update embedder API

---
 shell/platform/embedder/embedder.h | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index 22048c4eab516..b6946962936ba 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1381,6 +1381,11 @@ typedef struct FlutterEngineMappingPrivate* FlutterEngineMapping;
 /// If the asset was found and successfully loaded, return a valid
 /// `FlutterEngineMapping`. Otherwise return NULL to indicate an error occurred 
 /// while loading the asset.
+///
+/// Note that the returned `FlutterEngineMapping` is owned by the Engine and should
+/// be cached or reused. Each callback invocation must return a new 
+/// FlutterEngineMapping. Multiple mappings may refer to the same area in memory,
+/// proper book-keeping is up to the embedder.
 typedef FlutterEngineMapping (*FlutterAssetResolverGetAssetCallback)(const char* /* asset_name */,
                                                                       void* /* user_data */);
 
@@ -1390,6 +1395,10 @@ typedef struct {
   /// The size of the struct. Must be sizeof(FlutterEngineAssetResolver).
   size_t struct_size;
 
+  /// An opaque baton passed back to the embedder when a callback is
+  /// invoked. The engine does not interpret this field in any way.
+  void* user_data;
+
   /// Required. Gets and returns an asset if available. See the documentation on
   /// `FlutterAssetResolverGetAssetCallback` for more information.
   FlutterAssetResolverGetAssetCallback get_asset;
@@ -1402,7 +1411,11 @@ typedef struct {
   /// string can be collected after the call to `FlutterEngineRun` returns. The
   /// string must be NULL terminated.
   ///
-  /// If `asset_resolver` is provided, this path is ignored and may be NULL.
+  /// If `asset_resolver` is provided, may be NULL.
+  ///
+  /// If both `asset_resolver` and `assets_path` are provided, the `asset_resolver`
+  /// comes first in the asset search order, then `assets_path`. This effectively
+  /// makes `asset_resolver` an overlay over `assets_path`.
   const char* assets_path;
   /// The path to the Dart file containing the `main` entry point.
   /// The string can be collected after the call to `FlutterEngineRun` returns.
@@ -1644,7 +1657,11 @@ typedef struct {
 
   /// An asset resolver that fetches assets for the Engine.
   ///
-  /// If provided, this replaces the default asset resolver.
+  /// If `assets_path` is provided, may be NULL.
+  ///
+  /// If both `asset_resolver` and `assets_path` are provided, the `asset_resolver`
+  /// comes first in the asset search order, then `assets_path`. This effectively
+  /// makes `asset_resolver` an overlay over `assets_path`.
   const FlutterEngineAssetResolver* asset_resolver;
 } FlutterProjectArgs;
 

From 9b58de042b40200ddac799cf1764346ec6779184 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 17 Nov 2021 14:32:32 -0800
Subject: [PATCH 05/17] Add support for embedder-provided asset resolvers

---
 assets/asset_resolver.h                       |  3 +-
 shell/platform/embedder/BUILD.gn              |  2 +
 shell/platform/embedder/embedder.cc           | 41 +++++++++----
 .../embedder/embedder_asset_resolver.cc       | 58 +++++++++++++++++++
 .../embedder/embedder_asset_resolver.h        | 17 ++++++
 5 files changed, 110 insertions(+), 11 deletions(-)
 create mode 100644 shell/platform/embedder/embedder_asset_resolver.cc
 create mode 100644 shell/platform/embedder/embedder_asset_resolver.h

diff --git a/assets/asset_resolver.h b/assets/asset_resolver.h
index 4bf1eeb23e6f1..e5da2a2eb4a9a 100644
--- a/assets/asset_resolver.h
+++ b/assets/asset_resolver.h
@@ -26,7 +26,8 @@ class AssetResolver {
   enum AssetResolverType {
     kAssetManager,
     kApkAssetProvider,
-    kDirectoryAssetBundle
+    kDirectoryAssetBundle,
+    kEmbedderAssetResolver
   };
 
   virtual bool IsValid() const = 0;
diff --git a/shell/platform/embedder/BUILD.gn b/shell/platform/embedder/BUILD.gn
index b07e1bfa387b4..aacf0f2aafdc6 100644
--- a/shell/platform/embedder/BUILD.gn
+++ b/shell/platform/embedder/BUILD.gn
@@ -32,6 +32,8 @@ template("embedder_source_set") {
   source_set(target_name) {
     sources = [
       "embedder.cc",
+      "embedder_asset_resolver.cc",
+      "embedder_asset_resolver.h",
       "embedder_engine.cc",
       "embedder_engine.h",
       "embedder_external_texture_resolver.cc",
diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index be951f030fb34..80d736e0cfb03 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -47,6 +47,7 @@ extern const intptr_t kPlatformStrongDillSize;
 #include "flutter/shell/common/rasterizer.h"
 #include "flutter/shell/common/switches.h"
 #include "flutter/shell/platform/embedder/embedder.h"
+#include "flutter/shell/platform/embedder/embedder_asset_resolver.h"
 #include "flutter/shell/platform/embedder/embedder_engine.h"
 #include "flutter/shell/platform/embedder/embedder_external_texture_resolver.h"
 #include "flutter/shell/platform/embedder/embedder_mapping.h"
@@ -927,10 +928,10 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
                               "The Flutter project arguments were missing.");
   }
 
-  if (SAFE_ACCESS(args, assets_path, nullptr) == nullptr) {
+  if (SAFE_ACCESS(args, assets_path, nullptr) == nullptr && SAFE_ACCESS(args, asset_resolver, nullptr) == nullptr) {
     return LOG_EMBEDDER_ERROR(
         kInvalidArguments,
-        "The assets path in the Flutter project arguments was missing.");
+        "The assets path or asset resolver in the Flutter project arguments was missing.");
   }
 
   if (SAFE_ACCESS(args, main_path__unused__, nullptr) != nullptr) {
@@ -988,19 +989,22 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
   PopulateSnapshotMappingCallbacks(args, settings);
 
   settings.icu_data_path = icu_data_path;
-  settings.assets_path = args->assets_path;
+  if (args->assets_path) settings.assets_path = args->assets_path;
   settings.leak_vm = !SAFE_ACCESS(args, shutdown_dart_vm_when_done, false);
   settings.old_gen_heap_size = SAFE_ACCESS(args, dart_old_gen_heap_size, -1);
 
   if (!flutter::DartVM::IsRunningPrecompiledCode()) {
     // Verify the assets path contains Dart 2 kernel assets.
+    // NOTE: This check is skipped if using a custom asset resolver.
     const std::string kApplicationKernelSnapshotFileName = "kernel_blob.bin";
-    std::string application_kernel_path = fml::paths::JoinPaths(
-        {settings.assets_path, kApplicationKernelSnapshotFileName});
-    if (!fml::IsFile(application_kernel_path)) {
-      return LOG_EMBEDDER_ERROR(
-          kInvalidArguments,
-          "Not running in AOT mode but could not resolve the kernel binary.");
+    if (args->assets_path) {
+      std::string application_kernel_path = fml::paths::JoinPaths(
+          {settings.assets_path, kApplicationKernelSnapshotFileName});
+      if (!fml::IsFile(application_kernel_path)) {
+        return LOG_EMBEDDER_ERROR(
+            kInvalidArguments,
+            "Not running in AOT mode but could not resolve the kernel binary.");
+      }
     }
     settings.application_kernel_asset = kApplicationKernelSnapshotFileName;
   }
@@ -1297,8 +1301,25 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
                               "Task runner configuration was invalid.");
   }
 
+  auto asset_manager = std::make_shared<flutter::AssetManager>();
+
+  if (SAFE_ACCESS(args, asset_resolver, nullptr) != nullptr) {
+    asset_manager->PushBack(flutter::CreateEmbedderAssetResolver(args->asset_resolver));
+  }
+
+  if (args->assets_path) {
+    asset_manager->PushBack(std::make_unique<flutter::DirectoryAssetBundle>(
+        fml::OpenDirectory(args->assets_path, false,
+                           fml::FilePermission::kRead),
+        true));
+  }
+
   auto run_configuration =
-      flutter::RunConfiguration::InferFromSettings(settings);
+      flutter::RunConfiguration(
+        flutter::IsolateConfiguration::InferFromSettings(settings, asset_manager,
+                                                  nullptr),
+        asset_manager
+      );
 
   if (SAFE_ACCESS(args, custom_dart_entrypoint, nullptr) != nullptr) {
     auto dart_entrypoint = std::string{args->custom_dart_entrypoint};
diff --git a/shell/platform/embedder/embedder_asset_resolver.cc b/shell/platform/embedder/embedder_asset_resolver.cc
new file mode 100644
index 0000000000000..43ad9080826ec
--- /dev/null
+++ b/shell/platform/embedder/embedder_asset_resolver.cc
@@ -0,0 +1,58 @@
+// 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.
+
+#include "flutter/shell/platform/embedder/embedder_asset_resolver.h"
+#include "flutter/shell/platform/embedder/embedder_struct_macros.h"
+
+namespace flutter {
+
+class EmbedderAssetResolver final : public flutter::AssetResolver {
+  public:
+  explicit EmbedderAssetResolver(void* user_data,
+                                 FlutterAssetResolverGetAssetCallback get_asset)
+      : user_data_(user_data),
+        get_asset_(get_asset) {}
+  
+  ~EmbedderAssetResolver() override {}
+
+  // |AssetResolver|
+  bool IsValid() const override {
+    return true;
+  }
+
+  // |AssetResolver|
+  bool IsValidAfterAssetManagerChange() const override {
+    return true;
+  }
+
+  // |AssetResolver|
+  AssetResolverType GetType() const override {
+    return AssetResolverType::kEmbedderAssetResolver;
+  }
+
+  // |AssetResolver|
+  std::unique_ptr<fml::Mapping> GetAsMapping(const std::string& asset_name) const override {
+    if (!get_asset_) {
+      return std::unique_ptr<fml::Mapping>();
+    }
+
+    FlutterEngineMapping mapping = get_asset_(asset_name.c_str(), user_data_);
+    return std::unique_ptr<fml::Mapping>(reinterpret_cast<fml::Mapping*>(mapping));
+  }
+
+private:
+  void* user_data_;
+  FlutterAssetResolverGetAssetCallback get_asset_;
+  
+  FML_DISALLOW_COPY_AND_ASSIGN(EmbedderAssetResolver);
+};
+
+std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(const FlutterEngineAssetResolver* resolver) {
+  return std::make_unique<EmbedderAssetResolver>(
+    SAFE_ACCESS(resolver, user_data, nullptr),
+    SAFE_ACCESS(resolver, get_asset, nullptr)
+  );
+}
+
+}  // namespace flutter
diff --git a/shell/platform/embedder/embedder_asset_resolver.h b/shell/platform/embedder/embedder_asset_resolver.h
new file mode 100644
index 0000000000000..2b2c9d058c0f2
--- /dev/null
+++ b/shell/platform/embedder/embedder_asset_resolver.h
@@ -0,0 +1,17 @@
+// 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.
+
+#ifndef FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_ASSET_RESOLVER_H_
+#define FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_ASSET_RESOLVER_H_
+
+#include "flutter/assets/asset_resolver.h"
+#include "flutter/shell/platform/embedder/embedder.h"
+
+namespace flutter {
+
+std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(const FlutterEngineAssetResolver* resolver);
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_ASSET_RESOLVER_H_

From 8eb8d57eefa72e0a38fce45910b9e949eb6b3181 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 17 Nov 2021 14:38:07 -0800
Subject: [PATCH 06/17] Add tests for custom asset resolvers

---
 shell/platform/embedder/fixtures/main.dart    | 22 +++++
 .../embedder/tests/embedder_config_builder.cc |  5 +
 .../embedder/tests/embedder_config_builder.h  |  3 +
 .../embedder/tests/embedder_unittests.cc      | 98 +++++++++++++++++++
 4 files changed, 128 insertions(+)

diff --git a/shell/platform/embedder/fixtures/main.dart b/shell/platform/embedder/fixtures/main.dart
index 5196f37727597..7649378e75144 100644
--- a/shell/platform/embedder/fixtures/main.dart
+++ b/shell/platform/embedder/fixtures/main.dart
@@ -299,6 +299,28 @@ void null_platform_messages() {
   signalNativeTest();
 }
 
+const String channel = 'flutter/assets';
+ByteData encodePath(String path) => ByteData.sublistView(utf8.encoder.convert(path));
+
+void handleAssetReply(ByteData? reply) {
+  if (reply != null) {
+    signalNativeCount(reply.lengthInBytes);
+    signalNativeMessage(utf8.decode(Uint8List.sublistView(reply)));
+  } else {
+    signalNativeCount(-1);
+  }
+}
+
+@pragma('vm:entry-point')
+void existing_asset() {
+  PlatformDispatcher.instance.sendPlatformMessage(channel, encodePath('existing_asset'), handleAssetReply);
+}
+
+@pragma('vm:entry-point')
+void invalid_asset() {
+  PlatformDispatcher.instance.sendPlatformMessage(channel, encodePath('invalid_asset'), handleAssetReply);
+}
+
 Picture CreateSimplePicture() {
   Paint blackPaint = Paint();
   PictureRecorder baseRecorder = PictureRecorder();
diff --git a/shell/platform/embedder/tests/embedder_config_builder.cc b/shell/platform/embedder/tests/embedder_config_builder.cc
index d04188e0d3070..fcd1bb683373c 100644
--- a/shell/platform/embedder/tests/embedder_config_builder.cc
+++ b/shell/platform/embedder/tests/embedder_config_builder.cc
@@ -174,6 +174,11 @@ void EmbedderConfigBuilder::SetAssetsPath() {
   project_args_.assets_path = context_.GetAssetsPath().c_str();
 }
 
+void EmbedderConfigBuilder::SetAssetResolver(const FlutterEngineAssetResolver* resolver) {
+  asset_resolver_ = *resolver;
+  project_args_.asset_resolver = &asset_resolver_;
+}
+
 void EmbedderConfigBuilder::SetSnapshots() {
   if (auto mapping = context_.GetVMSnapshotData()) {
     project_args_.vm_snapshot_data = mapping->GetMapping();
diff --git a/shell/platform/embedder/tests/embedder_config_builder.h b/shell/platform/embedder/tests/embedder_config_builder.h
index ee1fb514bb611..1938299d2d390 100644
--- a/shell/platform/embedder/tests/embedder_config_builder.h
+++ b/shell/platform/embedder/tests/embedder_config_builder.h
@@ -65,6 +65,8 @@ class EmbedderConfigBuilder {
 
   void SetAssetsPath();
 
+  void SetAssetResolver(const FlutterEngineAssetResolver* resolver);
+
   void SetSnapshots();
 
   void SetAOTDataElf();
@@ -124,6 +126,7 @@ class EmbedderConfigBuilder {
   std::string dart_entrypoint_;
   FlutterCustomTaskRunners custom_task_runners_ = {};
   FlutterCompositor compositor_ = {};
+  FlutterEngineAssetResolver asset_resolver_ = {};
   std::vector<std::string> command_line_arguments_;
   std::vector<std::string> dart_entrypoint_arguments_;
   std::string log_tag_;
diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
index 3108cff91e200..55b6efcb13349 100644
--- a/shell/platform/embedder/tests/embedder_unittests.cc
+++ b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -474,6 +474,104 @@ TEST_F(EmbedderTest, InvalidPlatformMessages) {
   ASSERT_EQ(result, kInvalidArguments);
 }
 
+//------------------------------------------------------------------------------
+/// Tests that an asset can be loaded from a custom asset resolver.
+///
+TEST_F(EmbedderTest, CustomAssetResolverReturnsValidAsset) {
+  auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
+  EmbedderConfigBuilder builder(context);
+  builder.SetSoftwareRendererConfig();
+  builder.SetDartEntrypoint("existing_asset");
+
+  fml::AutoResetWaitableEvent destroy;
+
+  FlutterEngineAssetResolver resolver = {};
+  resolver.struct_size = sizeof(FlutterEngineAssetResolver);
+  resolver.user_data = reinterpret_cast<void*>(&destroy);
+  resolver.get_asset = [](const char* asset, void* user_data) -> FlutterEngineMapping {
+    if (strcmp(asset, "existing_asset") == 0) {
+      // Return an asset with the string "hello" as its contents.
+      // When the mapping is destroyed (on GC or Engine shutdown) the
+      // `destroy` event is signaled.
+      FlutterEngineMappingCreateInfo create_info = {};
+      FlutterEngineMapping out = nullptr;
+      create_info.struct_size = sizeof(FlutterEngineMappingCreateInfo);
+      create_info.data = reinterpret_cast<const uint8_t*>("hello");
+      create_info.data_size = 5;
+      create_info.user_data = user_data;
+      create_info.destruction_callback = [](void* user_data) {
+        reinterpret_cast<fml::AutoResetWaitableEvent*>(user_data)->Signal();
+      };
+      auto result = FlutterEngineCreateMapping(&create_info, &out);
+      EXPECT_EQ(result, kSuccess);
+      return out;
+    }
+    return nullptr;
+  };
+
+  builder.SetAssetResolver(&resolver);
+
+  fml::AutoResetWaitableEvent message;
+  context.AddNativeCallback(
+      "SignalNativeCount",
+      CREATE_NATIVE_ENTRY([](Dart_NativeArguments args) {
+        auto count = tonic::DartConverter<int64_t>::FromDart(
+            Dart_GetNativeArgument(args, 0));
+        // Dart should receive a 5 byte message reply.
+        EXPECT_EQ(5, count);
+      }));
+  context.AddNativeCallback(
+      "SignalNativeMessage",
+      CREATE_NATIVE_ENTRY(([&message](Dart_NativeArguments args) {
+        auto received_message = tonic::DartConverter<std::string>::FromDart(
+            Dart_GetNativeArgument(args, 0));
+        // The message received from the asset channel should be the string "hello".
+        EXPECT_EQ("hello", received_message);
+        message.Signal();
+      })));
+
+  {
+    auto engine = builder.LaunchEngine();
+    ASSERT_TRUE(engine.is_valid());
+    message.Wait();
+  }
+  // Before or during Engine shutdown, the mapping should be destroyed.
+  destroy.Wait();
+}
+
+//------------------------------------------------------------------------------
+/// Tests that an asset that aren't found return null responses.
+///
+TEST_F(EmbedderTest, CustomAssetResolverReturnsInvalidAsset) {
+  auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
+  EmbedderConfigBuilder builder(context);
+  builder.SetSoftwareRendererConfig();
+  builder.SetDartEntrypoint("invalid_asset");
+
+  FlutterEngineAssetResolver resolver = {};
+  resolver.struct_size = sizeof(FlutterEngineAssetResolver);
+  resolver.get_asset = [](const char* asset, void* user_data) -> FlutterEngineMapping {
+    return nullptr;
+  };
+
+  builder.SetAssetResolver(&resolver);
+
+  fml::AutoResetWaitableEvent message;
+  context.AddNativeCallback(
+      "SignalNativeCount",
+      CREATE_NATIVE_ENTRY([&message](Dart_NativeArguments args) {
+        auto count = tonic::DartConverter<int64_t>::FromDart(
+            Dart_GetNativeArgument(args, 0));
+        // Dart should receive a null reply.
+        EXPECT_EQ(-1, count);
+        message.Signal();
+      }));
+
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+  message.Wait();
+}
+
 //------------------------------------------------------------------------------
 /// Tests that setting a custom log callback works as expected and defaults to
 /// using tag "flutter".

From 50429c059b8cf8264bed8415abc83d47d21165db Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 17 Nov 2021 17:07:12 -0800
Subject: [PATCH 07/17] Fix formatting

---
 shell/platform/embedder/embedder.cc           | 28 ++++-----
 shell/platform/embedder/embedder.h            | 58 ++++++++++---------
 .../embedder/embedder_asset_resolver.cc       | 33 +++++------
 .../embedder/embedder_asset_resolver.h        |  3 +-
 shell/platform/embedder/embedder_mapping.cc   | 32 +++++-----
 shell/platform/embedder/embedder_mapping.h    |  3 +-
 .../embedder/tests/embedder_config_builder.cc |  3 +-
 .../embedder/tests/embedder_unittests.cc      | 12 ++--
 8 files changed, 87 insertions(+), 85 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index 80d736e0cfb03..dcfbcee9a83bf 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -928,10 +928,11 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
                               "The Flutter project arguments were missing.");
   }
 
-  if (SAFE_ACCESS(args, assets_path, nullptr) == nullptr && SAFE_ACCESS(args, asset_resolver, nullptr) == nullptr) {
-    return LOG_EMBEDDER_ERROR(
-        kInvalidArguments,
-        "The assets path or asset resolver in the Flutter project arguments was missing.");
+  if (SAFE_ACCESS(args, assets_path, nullptr) == nullptr &&
+      SAFE_ACCESS(args, asset_resolver, nullptr) == nullptr) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments,
+                              "The assets path or asset resolver in the "
+                              "Flutter project arguments was missing.");
   }
 
   if (SAFE_ACCESS(args, main_path__unused__, nullptr) != nullptr) {
@@ -989,7 +990,8 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
   PopulateSnapshotMappingCallbacks(args, settings);
 
   settings.icu_data_path = icu_data_path;
-  if (args->assets_path) settings.assets_path = args->assets_path;
+  if (args->assets_path)
+    settings.assets_path = args->assets_path;
   settings.leak_vm = !SAFE_ACCESS(args, shutdown_dart_vm_when_done, false);
   settings.old_gen_heap_size = SAFE_ACCESS(args, dart_old_gen_heap_size, -1);
 
@@ -1304,7 +1306,8 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
   auto asset_manager = std::make_shared<flutter::AssetManager>();
 
   if (SAFE_ACCESS(args, asset_resolver, nullptr) != nullptr) {
-    asset_manager->PushBack(flutter::CreateEmbedderAssetResolver(args->asset_resolver));
+    asset_manager->PushBack(
+        flutter::CreateEmbedderAssetResolver(args->asset_resolver));
   }
 
   if (args->assets_path) {
@@ -1314,12 +1317,10 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
         true));
   }
 
-  auto run_configuration =
-      flutter::RunConfiguration(
-        flutter::IsolateConfiguration::InferFromSettings(settings, asset_manager,
-                                                  nullptr),
-        asset_manager
-      );
+  auto run_configuration = flutter::RunConfiguration(
+      flutter::IsolateConfiguration::InferFromSettings(settings, asset_manager,
+                                                       nullptr),
+      asset_manager);
 
   if (SAFE_ACCESS(args, custom_dart_entrypoint, nullptr) != nullptr) {
     auto dart_entrypoint = std::string{args->custom_dart_entrypoint};
@@ -2385,7 +2386,8 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
 FlutterEngineResult FlutterEngineCreateMapping(
     const FlutterEngineMappingCreateInfo* create_info,
     FlutterEngineMapping* out_mapping) {
-  if (SAFE_ACCESS(create_info, data, nullptr) == nullptr && SAFE_ACCESS(create_info, data_size, 0) > 0) {
+  if (SAFE_ACCESS(create_info, data, nullptr) == nullptr &&
+      SAFE_ACCESS(create_info, data_size, 0) > 0) {
     return LOG_EMBEDDER_ERROR(kInvalidArguments, "Invalid mapping specified.");
   }
 
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index b6946962936ba..256621144a906 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1345,26 +1345,27 @@ typedef void (*FlutterLogMessageCallback)(const char* /* tag */,
 /// FlutterEngine instance in AOT mode.
 typedef struct _FlutterEngineAOTData* FlutterEngineAOTData;
 
-/// An immutable buffer of potentially shared data. 
+/// An immutable buffer of potentially shared data.
 typedef struct {
   /// The size of the struct. Must be sizeof(FlutterEngineMapping).
   size_t struct_size;
 
   /// A pointer to the data accessed by the Flutter Engine. The data will not be
-  /// mutated by the Flutter Engine, and must not be mutated by the Embedder until
-  /// the mapping is destroyed.
+  /// mutated by the Flutter Engine, and must not be mutated by the Embedder
+  /// until the mapping is destroyed.
   const uint8_t* data;
   /// The size of the data backed by this mapping. The data must be valid for
-  /// reading until this point. Bytes past the end are undefined and not accessed
-  /// by the Engine. 
+  /// reading until this point. Bytes past the end are undefined and not
+  /// accessed by the Engine.
   size_t data_size;
 
-  /// An opaque baton passed back to the embedder when the destruction_callback is
-  /// invoked. The engine does not interpret this field in any way.
+  /// An opaque baton passed back to the embedder when the destruction_callback
+  /// is invoked. The engine does not interpret this field in any way.
   void* user_data;
-  /// Called once by the engine to destroy this mapping. The `user_data` specified
-  /// above is passed in as the only argument. This call may mutate/free/unmap the
-  /// data, as it will no longer be accessed by the Flutter Engine.
+  /// Called once by the engine to destroy this mapping. The `user_data`
+  /// specified above is passed in as the only argument. This call may
+  /// mutate/free/unmap the data, as it will no longer be accessed by the
+  /// Flutter Engine.
   VoidCallback destruction_callback;
 } FlutterEngineMappingCreateInfo;
 
@@ -1375,22 +1376,23 @@ typedef struct FlutterEngineMappingPrivate* FlutterEngineMapping;
 /// This may be called by multiple threads.
 ///
 /// The `asset_name` parameter contains the path to the asset to load.
-/// `user_data` is the user data from `FlutterEngineAssetResolver`, registered via
-/// `FlutterProjectArgs`.
+/// `user_data` is the user data from `FlutterEngineAssetResolver`, registered
+/// via `FlutterProjectArgs`.
 ///
 /// If the asset was found and successfully loaded, return a valid
-/// `FlutterEngineMapping`. Otherwise return NULL to indicate an error occurred 
+/// `FlutterEngineMapping`. Otherwise return NULL to indicate an error occurred
 /// while loading the asset.
 ///
-/// Note that the returned `FlutterEngineMapping` is owned by the Engine and should
-/// be cached or reused. Each callback invocation must return a new 
-/// FlutterEngineMapping. Multiple mappings may refer to the same area in memory,
-/// proper book-keeping is up to the embedder.
-typedef FlutterEngineMapping (*FlutterAssetResolverGetAssetCallback)(const char* /* asset_name */,
-                                                                      void* /* user_data */);
+/// Note that the returned `FlutterEngineMapping` is owned by the Engine and
+/// should be cached or reused. Each callback invocation must return a new
+/// FlutterEngineMapping. Multiple mappings may refer to the same area in
+/// memory, proper book-keeping is up to the embedder.
+typedef FlutterEngineMapping (*FlutterAssetResolverGetAssetCallback)(
+    const char* /* asset_name */,
+    void* /* user_data */);
 
-/// Resolves assets on the behalf of the Flutter Engine, instead of accessing the
-/// filesystem directly.
+/// Resolves assets on the behalf of the Flutter Engine, instead of accessing
+/// the filesystem directly.
 typedef struct {
   /// The size of the struct. Must be sizeof(FlutterEngineAssetResolver).
   size_t struct_size;
@@ -1413,9 +1415,10 @@ typedef struct {
   ///
   /// If `asset_resolver` is provided, may be NULL.
   ///
-  /// If both `asset_resolver` and `assets_path` are provided, the `asset_resolver`
-  /// comes first in the asset search order, then `assets_path`. This effectively
-  /// makes `asset_resolver` an overlay over `assets_path`.
+  /// If both `asset_resolver` and `assets_path` are provided, the
+  /// `asset_resolver` comes first in the asset search order, then
+  /// `assets_path`. This effectively makes `asset_resolver` an overlay over
+  /// `assets_path`.
   const char* assets_path;
   /// The path to the Dart file containing the `main` entry point.
   /// The string can be collected after the call to `FlutterEngineRun` returns.
@@ -1659,9 +1662,10 @@ typedef struct {
   ///
   /// If `assets_path` is provided, may be NULL.
   ///
-  /// If both `asset_resolver` and `assets_path` are provided, the `asset_resolver`
-  /// comes first in the asset search order, then `assets_path`. This effectively
-  /// makes `asset_resolver` an overlay over `assets_path`.
+  /// If both `asset_resolver` and `assets_path` are provided, the
+  /// `asset_resolver` comes first in the asset search order, then
+  /// `assets_path`. This effectively makes `asset_resolver` an overlay over
+  /// `assets_path`.
   const FlutterEngineAssetResolver* asset_resolver;
 } FlutterProjectArgs;
 
diff --git a/shell/platform/embedder/embedder_asset_resolver.cc b/shell/platform/embedder/embedder_asset_resolver.cc
index 43ad9080826ec..191b35e6fc378 100644
--- a/shell/platform/embedder/embedder_asset_resolver.cc
+++ b/shell/platform/embedder/embedder_asset_resolver.cc
@@ -8,23 +8,18 @@
 namespace flutter {
 
 class EmbedderAssetResolver final : public flutter::AssetResolver {
-  public:
+ public:
   explicit EmbedderAssetResolver(void* user_data,
                                  FlutterAssetResolverGetAssetCallback get_asset)
-      : user_data_(user_data),
-        get_asset_(get_asset) {}
-  
+      : user_data_(user_data), get_asset_(get_asset) {}
+
   ~EmbedderAssetResolver() override {}
 
   // |AssetResolver|
-  bool IsValid() const override {
-    return true;
-  }
+  bool IsValid() const override { return true; }
 
   // |AssetResolver|
-  bool IsValidAfterAssetManagerChange() const override {
-    return true;
-  }
+  bool IsValidAfterAssetManagerChange() const override { return true; }
 
   // |AssetResolver|
   AssetResolverType GetType() const override {
@@ -32,27 +27,29 @@ class EmbedderAssetResolver final : public flutter::AssetResolver {
   }
 
   // |AssetResolver|
-  std::unique_ptr<fml::Mapping> GetAsMapping(const std::string& asset_name) const override {
+  std::unique_ptr<fml::Mapping> GetAsMapping(
+      const std::string& asset_name) const override {
     if (!get_asset_) {
       return std::unique_ptr<fml::Mapping>();
     }
 
     FlutterEngineMapping mapping = get_asset_(asset_name.c_str(), user_data_);
-    return std::unique_ptr<fml::Mapping>(reinterpret_cast<fml::Mapping*>(mapping));
+    return std::unique_ptr<fml::Mapping>(
+        reinterpret_cast<fml::Mapping*>(mapping));
   }
 
-private:
+ private:
   void* user_data_;
   FlutterAssetResolverGetAssetCallback get_asset_;
-  
+
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderAssetResolver);
 };
 
-std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(const FlutterEngineAssetResolver* resolver) {
+std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(
+    const FlutterEngineAssetResolver* resolver) {
   return std::make_unique<EmbedderAssetResolver>(
-    SAFE_ACCESS(resolver, user_data, nullptr),
-    SAFE_ACCESS(resolver, get_asset, nullptr)
-  );
+      SAFE_ACCESS(resolver, user_data, nullptr),
+      SAFE_ACCESS(resolver, get_asset, nullptr));
 }
 
 }  // namespace flutter
diff --git a/shell/platform/embedder/embedder_asset_resolver.h b/shell/platform/embedder/embedder_asset_resolver.h
index 2b2c9d058c0f2..34edd86bfdcf1 100644
--- a/shell/platform/embedder/embedder_asset_resolver.h
+++ b/shell/platform/embedder/embedder_asset_resolver.h
@@ -10,7 +10,8 @@
 
 namespace flutter {
 
-std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(const FlutterEngineAssetResolver* resolver);
+std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(
+    const FlutterEngineAssetResolver* resolver);
 
 }  // namespace flutter
 
diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
index 55917ff94cd34..ec6e981668cc6 100644
--- a/shell/platform/embedder/embedder_mapping.cc
+++ b/shell/platform/embedder/embedder_mapping.cc
@@ -8,7 +8,7 @@
 namespace flutter {
 
 class EmbedderMapping final : public fml::Mapping {
-  public:
+ public:
   EmbedderMapping(const uint8_t* data,
                   size_t size,
                   void* user_data,
@@ -17,27 +17,22 @@ class EmbedderMapping final : public fml::Mapping {
         size_(size),
         user_data_(user_data),
         destruction_callback_(destruction_callback) {}
-  
+
   ~EmbedderMapping() override {
-    if (destruction_callback_) destruction_callback_(user_data_);
+    if (destruction_callback_)
+      destruction_callback_(user_data_);
   }
 
   // |Mapping|
-  size_t GetSize() const override {
-    return size_;
-  }
+  size_t GetSize() const override { return size_; }
 
   // |Mapping|
-  const uint8_t* GetMapping() const override {
-    return data_;
-  }
+  const uint8_t* GetMapping() const override { return data_; }
 
   // |Mapping|
-  bool IsDontNeedSafe() const override {
-    return false;
-  }
+  bool IsDontNeedSafe() const override { return false; }
 
-private:
+ private:
   const uint8_t* data_;
   size_t size_;
   void* user_data_;
@@ -46,13 +41,12 @@ class EmbedderMapping final : public fml::Mapping {
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderMapping);
 };
 
-std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMappingCreateInfo* mapping) {
+std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
+    const FlutterEngineMappingCreateInfo* mapping) {
   return std::make_unique<EmbedderMapping>(
-    SAFE_ACCESS(mapping, data, nullptr),
-    SAFE_ACCESS(mapping, data_size, 0),
-    SAFE_ACCESS(mapping, user_data, nullptr),
-    SAFE_ACCESS(mapping, destruction_callback, nullptr)
-  );
+      SAFE_ACCESS(mapping, data, nullptr), SAFE_ACCESS(mapping, data_size, 0),
+      SAFE_ACCESS(mapping, user_data, nullptr),
+      SAFE_ACCESS(mapping, destruction_callback, nullptr));
 }
 
 }  // namespace flutter
diff --git a/shell/platform/embedder/embedder_mapping.h b/shell/platform/embedder/embedder_mapping.h
index 2315939af6e77..0ff69b603d03b 100644
--- a/shell/platform/embedder/embedder_mapping.h
+++ b/shell/platform/embedder/embedder_mapping.h
@@ -10,7 +10,8 @@
 
 namespace flutter {
 
-std::unique_ptr<fml::Mapping> CreateEmbedderMapping(const FlutterEngineMappingCreateInfo* mapping);
+std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
+    const FlutterEngineMappingCreateInfo* mapping);
 
 }  // namespace flutter
 
diff --git a/shell/platform/embedder/tests/embedder_config_builder.cc b/shell/platform/embedder/tests/embedder_config_builder.cc
index fcd1bb683373c..95bf7c5269fa4 100644
--- a/shell/platform/embedder/tests/embedder_config_builder.cc
+++ b/shell/platform/embedder/tests/embedder_config_builder.cc
@@ -174,7 +174,8 @@ void EmbedderConfigBuilder::SetAssetsPath() {
   project_args_.assets_path = context_.GetAssetsPath().c_str();
 }
 
-void EmbedderConfigBuilder::SetAssetResolver(const FlutterEngineAssetResolver* resolver) {
+void EmbedderConfigBuilder::SetAssetResolver(
+    const FlutterEngineAssetResolver* resolver) {
   asset_resolver_ = *resolver;
   project_args_.asset_resolver = &asset_resolver_;
 }
diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
index 55b6efcb13349..89efc60c76b1d 100644
--- a/shell/platform/embedder/tests/embedder_unittests.cc
+++ b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -488,7 +488,8 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsValidAsset) {
   FlutterEngineAssetResolver resolver = {};
   resolver.struct_size = sizeof(FlutterEngineAssetResolver);
   resolver.user_data = reinterpret_cast<void*>(&destroy);
-  resolver.get_asset = [](const char* asset, void* user_data) -> FlutterEngineMapping {
+  resolver.get_asset = [](const char* asset,
+                          void* user_data) -> FlutterEngineMapping {
     if (strcmp(asset, "existing_asset") == 0) {
       // Return an asset with the string "hello" as its contents.
       // When the mapping is destroyed (on GC or Engine shutdown) the
@@ -513,8 +514,7 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsValidAsset) {
 
   fml::AutoResetWaitableEvent message;
   context.AddNativeCallback(
-      "SignalNativeCount",
-      CREATE_NATIVE_ENTRY([](Dart_NativeArguments args) {
+      "SignalNativeCount", CREATE_NATIVE_ENTRY([](Dart_NativeArguments args) {
         auto count = tonic::DartConverter<int64_t>::FromDart(
             Dart_GetNativeArgument(args, 0));
         // Dart should receive a 5 byte message reply.
@@ -525,7 +525,8 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsValidAsset) {
       CREATE_NATIVE_ENTRY(([&message](Dart_NativeArguments args) {
         auto received_message = tonic::DartConverter<std::string>::FromDart(
             Dart_GetNativeArgument(args, 0));
-        // The message received from the asset channel should be the string "hello".
+        // The message received from the asset channel should be the string
+        // "hello".
         EXPECT_EQ("hello", received_message);
         message.Signal();
       })));
@@ -550,7 +551,8 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsInvalidAsset) {
 
   FlutterEngineAssetResolver resolver = {};
   resolver.struct_size = sizeof(FlutterEngineAssetResolver);
-  resolver.get_asset = [](const char* asset, void* user_data) -> FlutterEngineMapping {
+  resolver.get_asset = [](const char* asset,
+                          void* user_data) -> FlutterEngineMapping {
     return nullptr;
   };
 

From 769c6cf37632928b867719e8967c52eaf733badc Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Thu, 18 Nov 2021 15:03:01 -0800
Subject: [PATCH 08/17] Update licenses

---
 ci/licenses_golden/licenses_flutter | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index e0b43fca37cf5..88bc5d164105f 100755
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -1296,6 +1296,8 @@ FILE: ../../../flutter/shell/platform/embedder/assets/EmbedderInfo.plist
 FILE: ../../../flutter/shell/platform/embedder/assets/embedder.modulemap
 FILE: ../../../flutter/shell/platform/embedder/embedder.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder.h
+FILE: ../../../flutter/shell/platform/embedder/embedder_asset_resolver.cc
+FILE: ../../../flutter/shell/platform/embedder/embedder_asset_resolver.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_engine.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_engine.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_external_texture_gl.cc
@@ -1312,6 +1314,8 @@ FILE: ../../../flutter/shell/platform/embedder/embedder_include.c
 FILE: ../../../flutter/shell/platform/embedder/embedder_include2.c
 FILE: ../../../flutter/shell/platform/embedder/embedder_layers.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_layers.h
+FILE: ../../../flutter/shell/platform/embedder/embedder_mapping.cc
+FILE: ../../../flutter/shell/platform/embedder/embedder_mapping.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_render_target.cc

From 8d1f18f372b11dee3fd13432c191e54dd78a6224 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 12 Jan 2022 13:02:30 -0800
Subject: [PATCH 09/17] Rename FlutterEngineMapping to FlutterMapping

---
 shell/platform/embedder/embedder.cc           |  6 ++---
 shell/platform/embedder/embedder.h            | 24 +++++++++----------
 .../embedder/embedder_asset_resolver.cc       |  2 +-
 shell/platform/embedder/embedder_mapping.cc   |  2 +-
 shell/platform/embedder/embedder_mapping.h    |  2 +-
 5 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index dcfbcee9a83bf..7a2d0e00933b8 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -2384,15 +2384,15 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
 }
 
 FlutterEngineResult FlutterEngineCreateMapping(
-    const FlutterEngineMappingCreateInfo* create_info,
-    FlutterEngineMapping* out_mapping) {
+    const FlutterMappingCreateInfo* create_info,
+    FlutterMapping* out_mapping) {
   if (SAFE_ACCESS(create_info, data, nullptr) == nullptr &&
       SAFE_ACCESS(create_info, data_size, 0) > 0) {
     return LOG_EMBEDDER_ERROR(kInvalidArguments, "Invalid mapping specified.");
   }
 
   auto mapping = flutter::CreateEmbedderMapping(create_info);
-  *out_mapping = reinterpret_cast<FlutterEngineMapping>(mapping.release());
+  *out_mapping = reinterpret_cast<FlutterMapping>(mapping.release());
 
   return kSuccess;
 }
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index 256621144a906..330f37ad48b82 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1347,7 +1347,7 @@ typedef struct _FlutterEngineAOTData* FlutterEngineAOTData;
 
 /// An immutable buffer of potentially shared data.
 typedef struct {
-  /// The size of the struct. Must be sizeof(FlutterEngineMapping).
+  /// The size of the struct. Must be sizeof(FlutterMapping).
   size_t struct_size;
 
   /// A pointer to the data accessed by the Flutter Engine. The data will not be
@@ -1367,9 +1367,9 @@ typedef struct {
   /// mutate/free/unmap the data, as it will no longer be accessed by the
   /// Flutter Engine.
   VoidCallback destruction_callback;
-} FlutterEngineMappingCreateInfo;
+} FlutterMappingCreateInfo;
 
-typedef struct FlutterEngineMappingPrivate* FlutterEngineMapping;
+typedef struct FlutterMappingPrivate* FlutterMapping;
 
 /// Callback for fetching assets for a `FlutterEngineAssetResolver`.
 ///
@@ -1380,14 +1380,14 @@ typedef struct FlutterEngineMappingPrivate* FlutterEngineMapping;
 /// via `FlutterProjectArgs`.
 ///
 /// If the asset was found and successfully loaded, return a valid
-/// `FlutterEngineMapping`. Otherwise return NULL to indicate an error occurred
+/// `FlutterMapping`. Otherwise return NULL to indicate an error occurred
 /// while loading the asset.
 ///
-/// Note that the returned `FlutterEngineMapping` is owned by the Engine and
+/// Note that the returned `FlutterMapping` is owned by the Engine and
 /// should be cached or reused. Each callback invocation must return a new
-/// FlutterEngineMapping. Multiple mappings may refer to the same area in
+/// FlutterMapping. Multiple mappings may refer to the same area in
 /// memory, proper book-keeping is up to the embedder.
-typedef FlutterEngineMapping (*FlutterAssetResolverGetAssetCallback)(
+typedef FlutterMapping (*FlutterAssetResolverGetAssetCallback)(
     const char* /* asset_name */,
     void* /* user_data */);
 
@@ -2330,7 +2330,7 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
     size_t display_count);
 
 //------------------------------------------------------------------------------
-/// @brief      Creates a `FlutterEngineMapping` using the given creation info.
+/// @brief      Creates a `FlutterMapping` using the given creation info.
 ///             The backing memory is never mutated by the Engine, and must not
 ///             be mutated by the embedder until the mapping is destroyed.
 ///             The engine may access the mapping from multiple threads, and may
@@ -2343,8 +2343,8 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
 ///
 FLUTTER_EXPORT
 FlutterEngineResult FlutterEngineCreateMapping(
-    const FlutterEngineMappingCreateInfo* create_info,
-    FlutterEngineMapping* out_mapping);
+    const FlutterMappingCreateInfo* create_info,
+    FlutterMapping* out_mapping);
 
 #endif  // !FLUTTER_ENGINE_NO_PROTOTYPES
 
@@ -2463,8 +2463,8 @@ typedef FlutterEngineResult (*FlutterEngineNotifyDisplayUpdateFnPtr)(
     const FlutterEngineDisplay* displays,
     size_t display_count);
 typedef FlutterEngineResult (*FlutterEngineCreateMappingFnPtr)(
-    const FlutterEngineMappingCreateInfo* create_info,
-    FlutterEngineMapping* out_mapping);
+    const FlutterMappingCreateInfo* create_info,
+    FlutterMapping* out_mapping);
 
 /// Function-pointer-based versions of the APIs above.
 typedef struct {
diff --git a/shell/platform/embedder/embedder_asset_resolver.cc b/shell/platform/embedder/embedder_asset_resolver.cc
index 191b35e6fc378..ea960c0c20b63 100644
--- a/shell/platform/embedder/embedder_asset_resolver.cc
+++ b/shell/platform/embedder/embedder_asset_resolver.cc
@@ -33,7 +33,7 @@ class EmbedderAssetResolver final : public flutter::AssetResolver {
       return std::unique_ptr<fml::Mapping>();
     }
 
-    FlutterEngineMapping mapping = get_asset_(asset_name.c_str(), user_data_);
+    FlutterMapping mapping = get_asset_(asset_name.c_str(), user_data_);
     return std::unique_ptr<fml::Mapping>(
         reinterpret_cast<fml::Mapping*>(mapping));
   }
diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
index ec6e981668cc6..e8ceb19dcb33a 100644
--- a/shell/platform/embedder/embedder_mapping.cc
+++ b/shell/platform/embedder/embedder_mapping.cc
@@ -42,7 +42,7 @@ class EmbedderMapping final : public fml::Mapping {
 };
 
 std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
-    const FlutterEngineMappingCreateInfo* mapping) {
+    const FlutterMappingCreateInfo* mapping) {
   return std::make_unique<EmbedderMapping>(
       SAFE_ACCESS(mapping, data, nullptr), SAFE_ACCESS(mapping, data_size, 0),
       SAFE_ACCESS(mapping, user_data, nullptr),
diff --git a/shell/platform/embedder/embedder_mapping.h b/shell/platform/embedder/embedder_mapping.h
index 0ff69b603d03b..ec6eddaadc6e2 100644
--- a/shell/platform/embedder/embedder_mapping.h
+++ b/shell/platform/embedder/embedder_mapping.h
@@ -11,7 +11,7 @@
 namespace flutter {
 
 std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
-    const FlutterEngineMappingCreateInfo* mapping);
+    const FlutterMappingCreateInfo* mapping);
 
 }  // namespace flutter
 

From dbae453ab8f4126dacbd7d1c0ec236cf2c384895 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Thu, 13 Jan 2022 12:28:19 -0800
Subject: [PATCH 10/17] Add DestroyMapping and GetMappingData, improve docs

---
 shell/platform/embedder/embedder.cc         | 12 +++++
 shell/platform/embedder/embedder.h          | 56 ++++++++++++++++++---
 shell/platform/embedder/embedder_mapping.cc |  6 +--
 3 files changed, 64 insertions(+), 10 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index 7a2d0e00933b8..acec04d6264ab 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -2397,6 +2397,16 @@ FlutterEngineResult FlutterEngineCreateMapping(
   return kSuccess;
 }
 
+void FlutterEngineDestroyMapping(FlutterMapping mapping) {
+  delete reinterpret_cast<fml::Mapping*>(mapping);
+}
+
+const uint8_t* FlutterEngineGetMappingData(FlutterMapping mapping, size_t* out_size) {
+  auto fml_mapping = reinterpret_cast<fml::Mapping*>(mapping);
+  if (out_size != nullptr) *out_size = fml_mapping->GetSize();
+  return fml_mapping->GetMapping();
+}
+
 FlutterEngineResult FlutterEngineGetProcAddresses(
     FlutterEngineProcTable* table) {
   if (!table) {
@@ -2448,6 +2458,8 @@ FlutterEngineResult FlutterEngineGetProcAddresses(
            FlutterEnginePostCallbackOnAllNativeThreads);
   SET_PROC(NotifyDisplayUpdate, FlutterEngineNotifyDisplayUpdate);
   SET_PROC(CreateMapping, FlutterEngineCreateMapping);
+  SET_PROC(DestroyMapping, FlutterEngineDestroyMapping);
+  SET_PROC(GetMappingData, FlutterEngineGetMappingData);
 #undef SET_PROC
 
   return kSuccess;
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index 330f37ad48b82..b868bf303a038 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1345,6 +1345,16 @@ typedef void (*FlutterLogMessageCallback)(const char* /* tag */,
 /// FlutterEngine instance in AOT mode.
 typedef struct _FlutterEngineAOTData* FlutterEngineAOTData;
 
+// Callback called by the Engine to destroy a previously created FlutterMapping.
+//
+// The callback may be called on any thread, so it must be thread-safe.
+//
+// The `data`, `data_size`, and `user_data` parameters are the same values passed
+// in `FlutterEngineCreateMapping`.
+typedef void (*FlutterMappingDestroyCallback)(const uint8_t* /* data */,
+                                              size_t /* data_size */,
+                                              void* /* user_data */);
+
 /// An immutable buffer of potentially shared data.
 typedef struct {
   /// The size of the struct. Must be sizeof(FlutterMapping).
@@ -1362,11 +1372,11 @@ typedef struct {
   /// An opaque baton passed back to the embedder when the destruction_callback
   /// is invoked. The engine does not interpret this field in any way.
   void* user_data;
-  /// Called once by the engine to destroy this mapping. The `user_data`
-  /// specified above is passed in as the only argument. This call may
+  /// Called once by the engine to destroy this mapping. The `data`, `data_size`,
+  /// and `user_data` are passed into the given callback. This call may
   /// mutate/free/unmap the data, as it will no longer be accessed by the
   /// Flutter Engine.
-  VoidCallback destruction_callback;
+  FlutterMappingDestroyCallback destruction_callback;
 } FlutterMappingCreateInfo;
 
 typedef struct FlutterMappingPrivate* FlutterMapping;
@@ -1384,9 +1394,9 @@ typedef struct FlutterMappingPrivate* FlutterMapping;
 /// while loading the asset.
 ///
 /// Note that the returned `FlutterMapping` is owned by the Engine and
-/// should be cached or reused. Each callback invocation must return a new
+/// shouldn't be cached or reused. Each callback invocation MUST return a new
 /// FlutterMapping. Multiple mappings may refer to the same area in
-/// memory, proper book-keeping is up to the embedder.
+/// memory, but proper book-keeping is up to the Embedder.
 typedef FlutterMapping (*FlutterAssetResolverGetAssetCallback)(
     const char* /* asset_name */,
     void* /* user_data */);
@@ -2331,9 +2341,14 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
 
 //------------------------------------------------------------------------------
 /// @brief      Creates a `FlutterMapping` using the given creation info.
+///             The returned mapping is owned by the Embedder until passed to the
+///             Engine.
+///             
+///             When owned by the Engine:
+///             
 ///             The backing memory is never mutated by the Engine, and must not
-///             be mutated by the embedder until the mapping is destroyed.
-///             The engine may access the mapping from multiple threads, and may
+///             be mutated by the Embedder until the mapping is destroyed.
+///             The Engine may access the mapping from multiple threads, and may
 ///             destroy the mapping from any thread.
 ///
 /// @param[in]  create_info     Struct describing the mapping to create.
@@ -2346,6 +2361,29 @@ FlutterEngineResult FlutterEngineCreateMapping(
     const FlutterMappingCreateInfo* create_info,
     FlutterMapping* out_mapping);
 
+//------------------------------------------------------------------------------
+/// @brief      Destroys a `FlutterMapping` owned by the Embedder.
+///             This may be called by any thread, as long as the Engine doesn't
+///             own the mapping.
+///
+/// @param[in]  mapping     The mapping owned by the Embedder to destroy.
+///
+FLUTTER_EXPORT
+void FlutterEngineDestroyMapping(FlutterMapping mapping);
+
+//------------------------------------------------------------------------------
+/// @brief      Gets the data and size of a `FlutterMapping`.
+///             The mapping must be owned by the Embedder.
+///
+/// @param[in]  mapping         The mapping to get the data and size of.
+/// @param[out] out_size        Returns the mapping's size, if provided.
+///                             May be NULL.
+///
+/// @return     The address to the mapping's data.
+///
+FLUTTER_EXPORT
+const uint8_t* FlutterEngineGetMappingData(FlutterMapping mapping, size_t* out_size);
+
 #endif  // !FLUTTER_ENGINE_NO_PROTOTYPES
 
 // Typedefs for the function pointers in FlutterEngineProcTable.
@@ -2465,6 +2503,8 @@ typedef FlutterEngineResult (*FlutterEngineNotifyDisplayUpdateFnPtr)(
 typedef FlutterEngineResult (*FlutterEngineCreateMappingFnPtr)(
     const FlutterMappingCreateInfo* create_info,
     FlutterMapping* out_mapping);
+typedef void (*FlutterEngineDestroyMappingFnPtr)(FlutterMapping mapping);
+typedef const uint8_t* (*FlutterEngineGetMappingDataFnPtr)(FlutterMapping mapping, size_t* out_size);
 
 /// Function-pointer-based versions of the APIs above.
 typedef struct {
@@ -2510,6 +2550,8 @@ typedef struct {
       PostCallbackOnAllNativeThreads;
   FlutterEngineNotifyDisplayUpdateFnPtr NotifyDisplayUpdate;
   FlutterEngineCreateMappingFnPtr CreateMapping;
+  FlutterEngineDestroyMappingFnPtr DestroyMapping;
+  FlutterEngineGetMappingDataFnPtr GetMappingData;
 } FlutterEngineProcTable;
 
 //------------------------------------------------------------------------------
diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
index e8ceb19dcb33a..56ec35fde6f7c 100644
--- a/shell/platform/embedder/embedder_mapping.cc
+++ b/shell/platform/embedder/embedder_mapping.cc
@@ -12,7 +12,7 @@ class EmbedderMapping final : public fml::Mapping {
   EmbedderMapping(const uint8_t* data,
                   size_t size,
                   void* user_data,
-                  VoidCallback destruction_callback)
+                  FlutterMappingDestroyCallback destruction_callback)
       : data_(data),
         size_(size),
         user_data_(user_data),
@@ -20,7 +20,7 @@ class EmbedderMapping final : public fml::Mapping {
 
   ~EmbedderMapping() override {
     if (destruction_callback_)
-      destruction_callback_(user_data_);
+      destruction_callback_(data_, size_, user_data_);
   }
 
   // |Mapping|
@@ -36,7 +36,7 @@ class EmbedderMapping final : public fml::Mapping {
   const uint8_t* data_;
   size_t size_;
   void* user_data_;
-  VoidCallback destruction_callback_;
+  FlutterMappingDestroyCallback destruction_callback_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderMapping);
 };

From 775ecf5bd260876fa60ee16d3af6931ad1db042f Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Thu, 13 Jan 2022 12:30:54 -0800
Subject: [PATCH 11/17] Update formatting

---
 shell/platform/embedder/embedder.cc |  6 ++++--
 shell/platform/embedder/embedder.h  | 25 ++++++++++++++-----------
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index acec04d6264ab..b359a650aa63a 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -2401,9 +2401,11 @@ void FlutterEngineDestroyMapping(FlutterMapping mapping) {
   delete reinterpret_cast<fml::Mapping*>(mapping);
 }
 
-const uint8_t* FlutterEngineGetMappingData(FlutterMapping mapping, size_t* out_size) {
+const uint8_t* FlutterEngineGetMappingData(FlutterMapping mapping,
+                                           size_t* out_size) {
   auto fml_mapping = reinterpret_cast<fml::Mapping*>(mapping);
-  if (out_size != nullptr) *out_size = fml_mapping->GetSize();
+  if (out_size != nullptr)
+    *out_size = fml_mapping->GetSize();
   return fml_mapping->GetMapping();
 }
 
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index b868bf303a038..6a2e2655defe7 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1349,8 +1349,8 @@ typedef struct _FlutterEngineAOTData* FlutterEngineAOTData;
 //
 // The callback may be called on any thread, so it must be thread-safe.
 //
-// The `data`, `data_size`, and `user_data` parameters are the same values passed
-// in `FlutterEngineCreateMapping`.
+// The `data`, `data_size`, and `user_data` parameters are the same values
+// passed in `FlutterEngineCreateMapping`.
 typedef void (*FlutterMappingDestroyCallback)(const uint8_t* /* data */,
                                               size_t /* data_size */,
                                               void* /* user_data */);
@@ -1372,9 +1372,9 @@ typedef struct {
   /// An opaque baton passed back to the embedder when the destruction_callback
   /// is invoked. The engine does not interpret this field in any way.
   void* user_data;
-  /// Called once by the engine to destroy this mapping. The `data`, `data_size`,
-  /// and `user_data` are passed into the given callback. This call may
-  /// mutate/free/unmap the data, as it will no longer be accessed by the
+  /// Called once by the engine to destroy this mapping. The `data`,
+  /// `data_size`, and `user_data` are passed into the given callback. This call
+  /// may mutate/free/unmap the data, as it will no longer be accessed by the
   /// Flutter Engine.
   FlutterMappingDestroyCallback destruction_callback;
 } FlutterMappingCreateInfo;
@@ -2341,11 +2341,11 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
 
 //------------------------------------------------------------------------------
 /// @brief      Creates a `FlutterMapping` using the given creation info.
-///             The returned mapping is owned by the Embedder until passed to the
-///             Engine.
-///             
+///             The returned mapping is owned by the Embedder until passed to
+///             the Engine.
+///
 ///             When owned by the Engine:
-///             
+///
 ///             The backing memory is never mutated by the Engine, and must not
 ///             be mutated by the Embedder until the mapping is destroyed.
 ///             The Engine may access the mapping from multiple threads, and may
@@ -2382,7 +2382,8 @@ void FlutterEngineDestroyMapping(FlutterMapping mapping);
 /// @return     The address to the mapping's data.
 ///
 FLUTTER_EXPORT
-const uint8_t* FlutterEngineGetMappingData(FlutterMapping mapping, size_t* out_size);
+const uint8_t* FlutterEngineGetMappingData(FlutterMapping mapping,
+                                           size_t* out_size);
 
 #endif  // !FLUTTER_ENGINE_NO_PROTOTYPES
 
@@ -2504,7 +2505,9 @@ typedef FlutterEngineResult (*FlutterEngineCreateMappingFnPtr)(
     const FlutterMappingCreateInfo* create_info,
     FlutterMapping* out_mapping);
 typedef void (*FlutterEngineDestroyMappingFnPtr)(FlutterMapping mapping);
-typedef const uint8_t* (*FlutterEngineGetMappingDataFnPtr)(FlutterMapping mapping, size_t* out_size);
+typedef const uint8_t* (*FlutterEngineGetMappingDataFnPtr)(
+    FlutterMapping mapping,
+    size_t* out_size);
 
 /// Function-pointer-based versions of the APIs above.
 typedef struct {

From ae18e7e6610ac25d322832b786638da752e368df Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Thu, 13 Jan 2022 12:42:38 -0800
Subject: [PATCH 12/17] Use NonOwnedMapping instead of subclass

---
 shell/platform/embedder/embedder_mapping.cc | 46 ++++-----------------
 1 file changed, 9 insertions(+), 37 deletions(-)

diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
index 56ec35fde6f7c..2c627ba26a87b 100644
--- a/shell/platform/embedder/embedder_mapping.cc
+++ b/shell/platform/embedder/embedder_mapping.cc
@@ -7,46 +7,18 @@
 
 namespace flutter {
 
-class EmbedderMapping final : public fml::Mapping {
- public:
-  EmbedderMapping(const uint8_t* data,
-                  size_t size,
-                  void* user_data,
-                  FlutterMappingDestroyCallback destruction_callback)
-      : data_(data),
-        size_(size),
-        user_data_(user_data),
-        destruction_callback_(destruction_callback) {}
-
-  ~EmbedderMapping() override {
-    if (destruction_callback_)
-      destruction_callback_(data_, size_, user_data_);
-  }
-
-  // |Mapping|
-  size_t GetSize() const override { return size_; }
-
-  // |Mapping|
-  const uint8_t* GetMapping() const override { return data_; }
-
-  // |Mapping|
-  bool IsDontNeedSafe() const override { return false; }
-
- private:
-  const uint8_t* data_;
-  size_t size_;
-  void* user_data_;
-  FlutterMappingDestroyCallback destruction_callback_;
-
-  FML_DISALLOW_COPY_AND_ASSIGN(EmbedderMapping);
-};
-
 std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
     const FlutterMappingCreateInfo* mapping) {
-  return std::make_unique<EmbedderMapping>(
+  auto user_data = SAFE_ACCESS(mapping, user_data, nullptr);
+  auto destruction_callback =
+      SAFE_ACCESS(mapping, destruction_callback, nullptr);
+  return std::make_unique<fml::NonOwnedMapping>(
       SAFE_ACCESS(mapping, data, nullptr), SAFE_ACCESS(mapping, data_size, 0),
-      SAFE_ACCESS(mapping, user_data, nullptr),
-      SAFE_ACCESS(mapping, destruction_callback, nullptr));
+      [user_data, destruction_callback](const uint8_t* data, size_t size) {
+        if (destruction_callback) {
+          destruction_callback(data, size, user_data);
+        }
+      });
 }
 
 }  // namespace flutter

From b37a1a13721f1c54c48d3a3d020ed3c978f46113 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Tue, 18 Jan 2022 14:32:19 -0800
Subject: [PATCH 13/17] Remove embedder_mapping.cc

---
 shell/platform/embedder/BUILD.gn            |  2 --
 shell/platform/embedder/embedder.cc         | 19 ++++++++++++----
 shell/platform/embedder/embedder.h          |  2 +-
 shell/platform/embedder/embedder_mapping.cc | 24 ---------------------
 shell/platform/embedder/embedder_mapping.h  | 18 ----------------
 5 files changed, 16 insertions(+), 49 deletions(-)
 delete mode 100644 shell/platform/embedder/embedder_mapping.cc
 delete mode 100644 shell/platform/embedder/embedder_mapping.h

diff --git a/shell/platform/embedder/BUILD.gn b/shell/platform/embedder/BUILD.gn
index aacf0f2aafdc6..9caf914af3a08 100644
--- a/shell/platform/embedder/BUILD.gn
+++ b/shell/platform/embedder/BUILD.gn
@@ -46,8 +46,6 @@ template("embedder_source_set") {
       "embedder_include2.c",
       "embedder_layers.cc",
       "embedder_layers.h",
-      "embedder_mapping.cc",
-      "embedder_mapping.h",
       "embedder_platform_message_response.cc",
       "embedder_platform_message_response.h",
       "embedder_render_target.cc",
diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index b359a650aa63a..22cd912142e19 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -50,7 +50,6 @@ extern const intptr_t kPlatformStrongDillSize;
 #include "flutter/shell/platform/embedder/embedder_asset_resolver.h"
 #include "flutter/shell/platform/embedder/embedder_engine.h"
 #include "flutter/shell/platform/embedder/embedder_external_texture_resolver.h"
-#include "flutter/shell/platform/embedder/embedder_mapping.h"
 #include "flutter/shell/platform/embedder/embedder_platform_message_response.h"
 #include "flutter/shell/platform/embedder/embedder_render_target.h"
 #include "flutter/shell/platform/embedder/embedder_struct_macros.h"
@@ -2386,12 +2385,24 @@ FlutterEngineResult FlutterEngineNotifyDisplayUpdate(
 FlutterEngineResult FlutterEngineCreateMapping(
     const FlutterMappingCreateInfo* create_info,
     FlutterMapping* out_mapping) {
-  if (SAFE_ACCESS(create_info, data, nullptr) == nullptr &&
-      SAFE_ACCESS(create_info, data_size, 0) > 0) {
+  auto data = SAFE_ACCESS(create_info, data, nullptr);
+  auto data_size = SAFE_ACCESS(create_info, data_size, 0);
+  if (data == nullptr && data_size > 0) {
     return LOG_EMBEDDER_ERROR(kInvalidArguments, "Invalid mapping specified.");
   }
 
-  auto mapping = flutter::CreateEmbedderMapping(create_info);
+  auto user_data = SAFE_ACCESS(create_info, user_data, nullptr);
+  auto destruction_callback =
+      SAFE_ACCESS(create_info, destruction_callback, nullptr);
+
+  auto mapping = std::make_unique<fml::NonOwnedMapping>(
+      data, data_size,
+      [user_data, destruction_callback](const uint8_t* data, size_t size) {
+        if (destruction_callback) {
+          destruction_callback(data, size, user_data);
+        }
+      });
+
   *out_mapping = reinterpret_cast<FlutterMapping>(mapping.release());
 
   return kSuccess;
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index 6a2e2655defe7..bbd251a1fb598 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -1357,7 +1357,7 @@ typedef void (*FlutterMappingDestroyCallback)(const uint8_t* /* data */,
 
 /// An immutable buffer of potentially shared data.
 typedef struct {
-  /// The size of the struct. Must be sizeof(FlutterMapping).
+  /// The size of the struct. Must be sizeof(FlutterMappingCreateInfo).
   size_t struct_size;
 
   /// A pointer to the data accessed by the Flutter Engine. The data will not be
diff --git a/shell/platform/embedder/embedder_mapping.cc b/shell/platform/embedder/embedder_mapping.cc
deleted file mode 100644
index 2c627ba26a87b..0000000000000
--- a/shell/platform/embedder/embedder_mapping.cc
+++ /dev/null
@@ -1,24 +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.
-
-#include "flutter/shell/platform/embedder/embedder_mapping.h"
-#include "flutter/shell/platform/embedder/embedder_struct_macros.h"
-
-namespace flutter {
-
-std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
-    const FlutterMappingCreateInfo* mapping) {
-  auto user_data = SAFE_ACCESS(mapping, user_data, nullptr);
-  auto destruction_callback =
-      SAFE_ACCESS(mapping, destruction_callback, nullptr);
-  return std::make_unique<fml::NonOwnedMapping>(
-      SAFE_ACCESS(mapping, data, nullptr), SAFE_ACCESS(mapping, data_size, 0),
-      [user_data, destruction_callback](const uint8_t* data, size_t size) {
-        if (destruction_callback) {
-          destruction_callback(data, size, user_data);
-        }
-      });
-}
-
-}  // namespace flutter
diff --git a/shell/platform/embedder/embedder_mapping.h b/shell/platform/embedder/embedder_mapping.h
deleted file mode 100644
index ec6eddaadc6e2..0000000000000
--- a/shell/platform/embedder/embedder_mapping.h
+++ /dev/null
@@ -1,18 +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.
-
-#ifndef FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_MAPPING_H_
-#define FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_MAPPING_H_
-
-#include "flutter/fml/mapping.h"
-#include "flutter/shell/platform/embedder/embedder.h"
-
-namespace flutter {
-
-std::unique_ptr<fml::Mapping> CreateEmbedderMapping(
-    const FlutterMappingCreateInfo* mapping);
-
-}  // namespace flutter
-
-#endif  // FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_MAPPING_H_

From 558803ef9b35da565a3e91a07bc3c3d1a3c02c5f Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 19 Jan 2022 11:35:18 -0800
Subject: [PATCH 14/17] Use callback for embedder asset resolver

---
 shell/platform/embedder/embedder.cc             | 16 +++++++++++++++-
 .../embedder/embedder_asset_resolver.cc         | 17 ++++++-----------
 .../platform/embedder/embedder_asset_resolver.h |  6 +++++-
 3 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index 22cd912142e19..0b8376ef1d495 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -1305,8 +1305,22 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
   auto asset_manager = std::make_shared<flutter::AssetManager>();
 
   if (SAFE_ACCESS(args, asset_resolver, nullptr) != nullptr) {
+    auto resolver = args->asset_resolver;
+
+    auto user_data = SAFE_ACCESS(resolver, user_data, nullptr);
+    auto get_asset = SAFE_ACCESS(resolver, get_asset, nullptr);
+
+    if (get_asset == nullptr) {
+      return LOG_EMBEDDER_ERROR(kInvalidArguments,
+                                "Asset Resolver get_asset is null.");
+    }
+
     asset_manager->PushBack(
-        flutter::CreateEmbedderAssetResolver(args->asset_resolver));
+        flutter::CreateEmbedderAssetResolver([=](const char* asset_name) {
+          FlutterMapping mapping = get_asset(asset_name, user_data);
+          return std::unique_ptr<fml::Mapping>(
+            reinterpret_cast<fml::Mapping*>(mapping));
+        }));
   }
 
   if (args->assets_path) {
diff --git a/shell/platform/embedder/embedder_asset_resolver.cc b/shell/platform/embedder/embedder_asset_resolver.cc
index ea960c0c20b63..46d2695848bb7 100644
--- a/shell/platform/embedder/embedder_asset_resolver.cc
+++ b/shell/platform/embedder/embedder_asset_resolver.cc
@@ -9,9 +9,8 @@ namespace flutter {
 
 class EmbedderAssetResolver final : public flutter::AssetResolver {
  public:
-  explicit EmbedderAssetResolver(void* user_data,
-                                 FlutterAssetResolverGetAssetCallback get_asset)
-      : user_data_(user_data), get_asset_(get_asset) {}
+  explicit EmbedderAssetResolver(EmbedderAssetResolverGetAsset get_asset)
+      : get_asset_(get_asset) {}
 
   ~EmbedderAssetResolver() override {}
 
@@ -33,23 +32,19 @@ class EmbedderAssetResolver final : public flutter::AssetResolver {
       return std::unique_ptr<fml::Mapping>();
     }
 
-    FlutterMapping mapping = get_asset_(asset_name.c_str(), user_data_);
-    return std::unique_ptr<fml::Mapping>(
-        reinterpret_cast<fml::Mapping*>(mapping));
+    return get_asset_(asset_name.c_str());
   }
 
  private:
-  void* user_data_;
-  FlutterAssetResolverGetAssetCallback get_asset_;
+  EmbedderAssetResolverGetAsset get_asset_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderAssetResolver);
 };
 
 std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(
-    const FlutterEngineAssetResolver* resolver) {
+    EmbedderAssetResolverGetAsset get_asset) {
   return std::make_unique<EmbedderAssetResolver>(
-      SAFE_ACCESS(resolver, user_data, nullptr),
-      SAFE_ACCESS(resolver, get_asset, nullptr));
+      std::move(get_asset));
 }
 
 }  // namespace flutter
diff --git a/shell/platform/embedder/embedder_asset_resolver.h b/shell/platform/embedder/embedder_asset_resolver.h
index 34edd86bfdcf1..8b7609792905d 100644
--- a/shell/platform/embedder/embedder_asset_resolver.h
+++ b/shell/platform/embedder/embedder_asset_resolver.h
@@ -5,13 +5,17 @@
 #ifndef FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_ASSET_RESOLVER_H_
 #define FLUTTER_SHELL_PLATFORM_EMBEDDER_EMBEDDER_ASSET_RESOLVER_H_
 
+#include <functional>
+
 #include "flutter/assets/asset_resolver.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
 namespace flutter {
 
+using EmbedderAssetResolverGetAsset = std::function<std::unique_ptr<fml::Mapping>(const char* /* asset_name */)>;
+
 std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(
-    const FlutterEngineAssetResolver* resolver);
+    EmbedderAssetResolverGetAsset get_asset);
 
 }  // namespace flutter
 

From 726a752daaf0c8ba14b2b19922bfd133230e2c9e Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 19 Jan 2022 11:37:54 -0800
Subject: [PATCH 15/17] Fix test

---
 shell/platform/embedder/tests/embedder_unittests.cc | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
index 89efc60c76b1d..84fee78df70a0 100644
--- a/shell/platform/embedder/tests/embedder_unittests.cc
+++ b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -489,18 +489,18 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsValidAsset) {
   resolver.struct_size = sizeof(FlutterEngineAssetResolver);
   resolver.user_data = reinterpret_cast<void*>(&destroy);
   resolver.get_asset = [](const char* asset,
-                          void* user_data) -> FlutterEngineMapping {
+                          void* user_data) -> FlutterMapping {
     if (strcmp(asset, "existing_asset") == 0) {
       // Return an asset with the string "hello" as its contents.
       // When the mapping is destroyed (on GC or Engine shutdown) the
       // `destroy` event is signaled.
-      FlutterEngineMappingCreateInfo create_info = {};
-      FlutterEngineMapping out = nullptr;
-      create_info.struct_size = sizeof(FlutterEngineMappingCreateInfo);
+      FlutterMappingCreateInfo create_info = {};
+      FlutterMapping out = nullptr;
+      create_info.struct_size = sizeof(FlutterMappingCreateInfo);
       create_info.data = reinterpret_cast<const uint8_t*>("hello");
       create_info.data_size = 5;
       create_info.user_data = user_data;
-      create_info.destruction_callback = [](void* user_data) {
+      create_info.destruction_callback = [](const uint8_t* data, size_t size, void* user_data) {
         reinterpret_cast<fml::AutoResetWaitableEvent*>(user_data)->Signal();
       };
       auto result = FlutterEngineCreateMapping(&create_info, &out);
@@ -552,7 +552,7 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsInvalidAsset) {
   FlutterEngineAssetResolver resolver = {};
   resolver.struct_size = sizeof(FlutterEngineAssetResolver);
   resolver.get_asset = [](const char* asset,
-                          void* user_data) -> FlutterEngineMapping {
+                          void* user_data) -> FlutterMapping {
     return nullptr;
   };
 

From cafb95de5fe73aaea009f60cd24e77b4b089e046 Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 19 Jan 2022 12:03:03 -0800
Subject: [PATCH 16/17] Fix and format

---
 shell/platform/embedder/embedder.cc                 | 2 +-
 shell/platform/embedder/embedder_asset_resolver.cc  | 9 ++++-----
 shell/platform/embedder/embedder_asset_resolver.h   | 3 ++-
 shell/platform/embedder/tests/embedder_unittests.cc | 3 ++-
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index 0b8376ef1d495..c7f8c1fa6f030 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -1319,7 +1319,7 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
         flutter::CreateEmbedderAssetResolver([=](const char* asset_name) {
           FlutterMapping mapping = get_asset(asset_name, user_data);
           return std::unique_ptr<fml::Mapping>(
-            reinterpret_cast<fml::Mapping*>(mapping));
+              reinterpret_cast<fml::Mapping*>(mapping));
         }));
   }
 
diff --git a/shell/platform/embedder/embedder_asset_resolver.cc b/shell/platform/embedder/embedder_asset_resolver.cc
index 46d2695848bb7..6000f06e3ce12 100644
--- a/shell/platform/embedder/embedder_asset_resolver.cc
+++ b/shell/platform/embedder/embedder_asset_resolver.cc
@@ -12,10 +12,10 @@ class EmbedderAssetResolver final : public flutter::AssetResolver {
   explicit EmbedderAssetResolver(EmbedderAssetResolverGetAsset get_asset)
       : get_asset_(get_asset) {}
 
-  ~EmbedderAssetResolver() override {}
+  ~EmbedderAssetResolver() = default;
 
   // |AssetResolver|
-  bool IsValid() const override { return true; }
+  bool IsValid() const override { return (bool)get_asset_; }
 
   // |AssetResolver|
   bool IsValidAfterAssetManagerChange() const override { return true; }
@@ -29,7 +29,7 @@ class EmbedderAssetResolver final : public flutter::AssetResolver {
   std::unique_ptr<fml::Mapping> GetAsMapping(
       const std::string& asset_name) const override {
     if (!get_asset_) {
-      return std::unique_ptr<fml::Mapping>();
+      return nullptr;
     }
 
     return get_asset_(asset_name.c_str());
@@ -43,8 +43,7 @@ class EmbedderAssetResolver final : public flutter::AssetResolver {
 
 std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(
     EmbedderAssetResolverGetAsset get_asset) {
-  return std::make_unique<EmbedderAssetResolver>(
-      std::move(get_asset));
+  return std::make_unique<EmbedderAssetResolver>(std::move(get_asset));
 }
 
 }  // namespace flutter
diff --git a/shell/platform/embedder/embedder_asset_resolver.h b/shell/platform/embedder/embedder_asset_resolver.h
index 8b7609792905d..df73ee8baad25 100644
--- a/shell/platform/embedder/embedder_asset_resolver.h
+++ b/shell/platform/embedder/embedder_asset_resolver.h
@@ -12,7 +12,8 @@
 
 namespace flutter {
 
-using EmbedderAssetResolverGetAsset = std::function<std::unique_ptr<fml::Mapping>(const char* /* asset_name */)>;
+using EmbedderAssetResolverGetAsset =
+    std::function<std::unique_ptr<fml::Mapping>(const char* /* asset_name */)>;
 
 std::unique_ptr<flutter::AssetResolver> CreateEmbedderAssetResolver(
     EmbedderAssetResolverGetAsset get_asset);
diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
index 84fee78df70a0..390d017b45708 100644
--- a/shell/platform/embedder/tests/embedder_unittests.cc
+++ b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -500,7 +500,8 @@ TEST_F(EmbedderTest, CustomAssetResolverReturnsValidAsset) {
       create_info.data = reinterpret_cast<const uint8_t*>("hello");
       create_info.data_size = 5;
       create_info.user_data = user_data;
-      create_info.destruction_callback = [](const uint8_t* data, size_t size, void* user_data) {
+      create_info.destruction_callback = [](const uint8_t* data, size_t size,
+                                            void* user_data) {
         reinterpret_cast<fml::AutoResetWaitableEvent*>(user_data)->Signal();
       };
       auto result = FlutterEngineCreateMapping(&create_info, &out);

From e5bef6e4f9d63e634be74b108b5eaf6a37a1303f Mon Sep 17 00:00:00 2001
From: Dwayne Slater <ds84182@gmail.com>
Date: Wed, 19 Jan 2022 14:12:53 -0800
Subject: [PATCH 17/17] Update generated licenses

---
 ci/licenses_golden/licenses_flutter | 2 --
 1 file changed, 2 deletions(-)

diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index 88bc5d164105f..70aa98611bd53 100755
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -1314,8 +1314,6 @@ FILE: ../../../flutter/shell/platform/embedder/embedder_include.c
 FILE: ../../../flutter/shell/platform/embedder/embedder_include2.c
 FILE: ../../../flutter/shell/platform/embedder/embedder_layers.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_layers.h
-FILE: ../../../flutter/shell/platform/embedder/embedder_mapping.cc
-FILE: ../../../flutter/shell/platform/embedder/embedder_mapping.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_render_target.cc