[web] Start splitting the engine into smaller libs

ci/licenses_golden/licenses_flutter

@@ -519,6 +519,7 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/key_map.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/keyboard.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/keyboard_binding.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/mouse_cursor.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/history.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/url_strategy.dart
@@ -542,6 +543,7 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/semantics.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/semantics_helper.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/tappable.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/text_field.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/services.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/services/buffers.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/services/message_codec.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/services/message_codecs.dart

lib/web_ui/lib/src/engine.dart

@@ -5,8 +5,19 @@
 @JS()
 library engine;
 
+// This file is transformed during the build process in order to make it a
+// single library. Some notable transformations:
+//
+// 1. Imports of engine/* files are stripped out.
+// 2. Exports of engine/* files are replaced with a part directive.
+//
+// The code that performs the transformations lives in:
+// - https://github.com/flutter/engine/blob/master/web_sdk/sdk_rewriter.dart
+
 import 'dart:async';
 import 'dart:collection'
+    // Some of these names are used in services/buffers.dart for example.
+    // ignore: unused_shown_name
     show ListBase, IterableBase, DoubleLinkedQueue, DoubleLinkedQueueEntry;
 import 'dart:convert' hide Codec;
 import 'dart:developer' as developer;
@@ -21,10 +32,68 @@ import 'package:meta/meta.dart';
 
 import '../ui.dart' as ui;
 
-part 'engine/alarm_clock.dart';
+import 'engine/alarm_clock.dart';
+export 'engine/alarm_clock.dart';
+
+import 'engine/browser_detection.dart';
+export 'engine/browser_detection.dart';
+
+import 'engine/mouse_cursor.dart';
+export 'engine/mouse_cursor.dart';
+
+import 'engine/navigation/history.dart';
+export 'engine/navigation/history.dart';
+
+import 'engine/navigation/js_url_strategy.dart';
+export 'engine/navigation/js_url_strategy.dart';
+
+import 'engine/navigation/url_strategy.dart';
+export 'engine/navigation/url_strategy.dart';
+
+import 'engine/plugins.dart';
+export 'engine/plugins.dart';
+
+import 'engine/pointer_binding.dart';
+export 'engine/pointer_binding.dart';
+
+// This import is intentionally commented out because the analyzer says it's unused.
+// import 'engine/pointer_converter.dart';
+export 'engine/pointer_converter.dart';
+
+// This import is intentionally commented out because the analyzer says it's unused.
+// import 'engine/services/buffers.dart';
+export 'engine/services/buffers.dart';
+
+import 'engine/services/message_codec.dart';
+export 'engine/services/message_codec.dart';
+
+import 'engine/services/message_codecs.dart';
+export 'engine/services/message_codecs.dart';
+
+// This import is intentionally commented out because the analyzer says it's unused.
+// import 'engine/services/serialization.dart';
+export 'engine/services/serialization.dart';
+
+import 'engine/shadow.dart';
+export 'engine/shadow.dart';
+
+import 'engine/test_embedding.dart';
+export 'engine/test_embedding.dart';
+
+import 'engine/ulps.dart';
+export 'engine/ulps.dart';
+
+import 'engine/validators.dart';
+export 'engine/validators.dart';
+
+import 'engine/vector_math.dart';
+export 'engine/vector_math.dart';
+
+import 'engine/web_experiments.dart';
+export 'engine/web_experiments.dart';
+
 part 'engine/assets.dart';
 part 'engine/bitmap_canvas.dart';
-part 'engine/browser_detection.dart';
 part 'engine/canvaskit/canvas.dart';
 part 'engine/canvaskit/canvaskit_canvas.dart';
 part 'engine/canvaskit/canvaskit_api.dart';
@@ -63,9 +132,6 @@ part 'engine/dom_canvas.dart';
 part 'engine/dom_renderer.dart';
 part 'engine/engine_canvas.dart';
 part 'engine/frame_reference.dart';
-part 'engine/navigation/history.dart';
-part 'engine/navigation/js_url_strategy.dart';
-part 'engine/navigation/url_strategy.dart';
 part 'engine/html/backdrop_filter.dart';
 part 'engine/html/canvas.dart';
 part 'engine/html/clip.dart';
@@ -101,14 +167,10 @@ part 'engine/html_image_codec.dart';
 part 'engine/keyboard_binding.dart';
 part 'engine/keyboard.dart';
 part 'engine/key_map.dart';
-part 'engine/mouse_cursor.dart';
 part 'engine/onscreen_logging.dart';
 part 'engine/picture.dart';
 part 'engine/platform_dispatcher.dart';
 part 'engine/platform_views.dart';
-part 'engine/plugins.dart';
-part 'engine/pointer_binding.dart';
-part 'engine/pointer_converter.dart';
 part 'engine/profiler.dart';
 part 'engine/rrect_renderer.dart';
 part 'engine/semantics/accessibility.dart';
@@ -122,12 +184,6 @@ part 'engine/semantics/semantics.dart';
 part 'engine/semantics/semantics_helper.dart';
 part 'engine/semantics/tappable.dart';
 part 'engine/semantics/text_field.dart';
-part 'engine/services/buffers.dart';
-part 'engine/services/message_codec.dart';
-part 'engine/services/message_codecs.dart';
-part 'engine/services/serialization.dart';
-part 'engine/shadow.dart';
-part 'engine/test_embedding.dart';
 part 'engine/text/font_collection.dart';
 part 'engine/text/layout_service.dart';
 part 'engine/text/line_break_properties.dart';
@@ -144,11 +200,7 @@ part 'engine/text_editing/autofill_hint.dart';
 part 'engine/text_editing/input_type.dart';
 part 'engine/text_editing/text_capitalization.dart';
 part 'engine/text_editing/text_editing.dart';
-part 'engine/ulps.dart';
 part 'engine/util.dart';
-part 'engine/validators.dart';
-part 'engine/vector_math.dart';
-part 'engine/web_experiments.dart';
 part 'engine/window.dart';
 
 // The mode the app is running in.

lib/web_ui/lib/src/engine/alarm_clock.dart

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:async';
+
+import 'package:ui/ui.dart' as ui;
 
 /// A function that returns current system time.
 typedef TimestampFunction = DateTime Function();

lib/web_ui/lib/src/engine/browser_detection.dart

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:html' as html;
+
+import 'package:meta/meta.dart';
 
 /// The HTML engine used by the current browser.
 enum BrowserEngine {

lib/web_ui/lib/src/engine/mouse_cursor.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'package:ui/src/engine.dart' show domRenderer, DomRenderer;
 
 /// Provides mouse cursor bindings, such as the `flutter/mousecursor` channel.
 class MouseCursor {

lib/web_ui/lib/src/engine/navigation.dart

@@ -0,0 +1,8 @@
+// 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.
+
+// @dart = 2.12
+export 'navigation/history.dart';
+export 'navigation/js_url_strategy.dart';
+export 'navigation/url_strategy.dart';

lib/web_ui/lib/src/engine/navigation/history.dart

@@ -2,7 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:html' as html;
+
+import 'package:ui/src/engine.dart' show EnginePlatformDispatcher;
+import 'package:ui/ui.dart' as ui;
+
+import '../services/message_codec.dart';
+import '../services/message_codecs.dart';
+import 'url_strategy.dart';
 
 /// An abstract class that provides the API for [EngineWindow] to delegate its
 /// navigating events.

lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart

@@ -2,7 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+@JS()
+library js_url_strategy;
+
+import 'dart:html' as html;
+
+import 'package:js/js.dart';
+import 'package:ui/ui.dart' as ui;
 
 typedef _PathGetter = String Function();
 

lib/web_ui/lib/src/engine/navigation/url_strategy.dart

@@ -2,7 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:async';
+import 'dart:html' as html;
+
+import 'package:ui/ui.dart' as ui;
+
+import 'js_url_strategy.dart';
 
 /// Represents and reads route state from the browser's URL.
 ///

lib/web_ui/lib/src/engine/plugins.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:typed_data';
+
+import 'package:ui/ui.dart' as ui;
 
 Future<void> Function(String, ByteData?, ui.PlatformMessageResponseCallback?)? pluginMessageCallHandler;

lib/web_ui/lib/src/engine/pointer_binding.dart

@@ -2,7 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:html' as html;
+import 'dart:js' as js;
+import 'dart:js_util' as js_util;
+import 'dart:math' as math;
+
+import 'package:meta/meta.dart';
+import 'package:ui/src/engine.dart';
+import 'package:ui/ui.dart' as ui;
+
+import 'pointer_converter.dart';
 
 /// Set this flag to true to see all the fired events in the console.
 const bool _debugLogPointerEvents = false;

lib/web_ui/lib/src/engine/pointer_converter.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'package:ui/ui.dart' as ui;
 
 const bool _debugLogPointerConverter = false;
 

lib/web_ui/lib/src/engine/services.dart

@@ -0,0 +1,9 @@
+// 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.
+
+// @dart = 2.12
+export 'services/buffers.dart';
+export 'services/message_codec.dart';
+export 'services/message_codecs.dart';
+export 'services/serialization.dart';

lib/web_ui/lib/src/engine/services/buffers.dart

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:collection';
+import 'dart:typed_data';
 
 abstract class _TypedDataBuffer<E> extends ListBase<E> {
   static const int _initialLength = 8;

lib/web_ui/lib/src/engine/services/message_codec.dart

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:typed_data';
+
+import 'package:meta/meta.dart';
 
 /// A message encoding/decoding mechanism.
 ///

lib/web_ui/lib/src/engine/services/message_codecs.dart

@@ -2,7 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'message_codec.dart';
+import 'serialization.dart';
 
 /// [MessageCodec] with unencoded binary messages represented using [ByteData].
 ///

lib/web_ui/lib/src/engine/services/serialization.dart

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:typed_data';
+
+import 'buffers.dart';
 
 /// Write-only buffer for incrementally building a [ByteData] instance.
 ///

lib/web_ui/lib/src/engine/shadow.dart

@@ -2,7 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:html' as html;
+import 'dart:math' as math;
+
+import 'package:meta/meta.dart';
+import 'package:ui/ui.dart' as ui;
 
 /// How far is the light source from the surface of the UI.
 ///

lib/web_ui/lib/src/engine/test_embedding.dart

@@ -2,7 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:async';
+import 'dart:html' as html;
+
+import 'package:ui/ui.dart' as ui;
+
+import 'navigation/url_strategy.dart';
 
 const bool _debugLogHistoryActions = false;
 

lib/web_ui/lib/src/engine/ulps.dart

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:math' as math;
+import 'dart:typed_data';
 
 // This is a small library to handle stability for floating point operations.
 //

lib/web_ui/lib/src/engine/validators.dart

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:typed_data';
+
+import 'package:ui/ui.dart' as ui;
 
 bool rectIsValid(ui.Rect rect) {
   assert(rect != null, 'Rect argument was null.'); // ignore: unnecessary_null_comparison

lib/web_ui/lib/src/engine/vector_math.dart

@@ -2,7 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-part of engine;
+import 'dart:math' as math;
+import 'dart:typed_data';
+
+import 'package:ui/src/engine.dart' show assertionsEnabled;
 
 class Matrix4 {
   final Float32List _m4storage;