[web] Migrate web-only initialization APIs (#129856)

- `ui_web.warmupEngine`
- `ui_web.setPluginHandler`
- `ui_web.debugEmulateFlutterTesterEnvironment`

packages/flutter/lib/src/foundation/_platform_web.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.
 
-import 'dart:ui' as ui;
+import 'dart:ui_web' as ui_web;
 
 import '../services/dom.dart';
 
@@ -23,9 +23,7 @@ platform.TargetPlatform get defaultTargetPlatform {
 final platform.TargetPlatform? _testPlatform = () {
   platform.TargetPlatform? result;
   assert(() {
-    // This member is only available in the web's dart:ui implementation.
-    // ignore: undefined_prefixed_name
-    if (ui.debugEmulateFlutterTesterEnvironment as bool) {
+    if (ui_web.debugEmulateFlutterTesterEnvironment) {
       result = platform.TargetPlatform.android;
     }
     return true;

packages/flutter_tools/lib/src/web/bootstrap.dart

@@ -219,6 +219,7 @@ String generateTestEntrypoint({
   // @dart = ${languageVersion.major}.${languageVersion.minor}
   import 'org-dartlang-app:///$relativeTestPath' as test;
   import 'dart:ui' as ui;
+  import 'dart:ui_web' as ui_web;
   import 'dart:html';
   import 'dart:js';
   ${testConfigPath != null ? "import '${Uri.file(testConfigPath)}' as test_config;" : ""}
@@ -227,7 +228,7 @@ String generateTestEntrypoint({
   import 'package:test_api/backend.dart';
 
   Future<void> main() async {
-    ui.debugEmulateFlutterTesterEnvironment = true;
+    ui_web.debugEmulateFlutterTesterEnvironment = true;
     await ui.webOnlyInitializePlatform();
     webGoldenComparator = DefaultWebGoldenComparator(Uri.parse('${Uri.file(absolutePath)}'));
     (ui.window as dynamic).debugOverrideDevicePixelRatio(3.0);

packages/flutter_tools/lib/src/web/file_generators/main_dart.dart

@@ -19,7 +19,7 @@ String generateMainDartFile(String appEntrypoint, {
     '',
     '// ignore_for_file: type=lint',
     '',
-    "import 'dart:ui' as ui;",
+    "import 'dart:ui_web' as ui_web;",
     "import 'dart:async';",
     '',
     "import '$appEntrypoint' as entrypoint;",
@@ -29,7 +29,7 @@ String generateMainDartFile(String appEntrypoint, {
     'typedef _NullaryFunction = dynamic Function();',
     '',
     'Future<void> main() async {',
-    '  await ui.webOnlyWarmupEngine(',
+    '  await ui_web.bootstrapEngine(',
     '    runApp: () {',
     '      if (entrypoint.main is _UnaryFunction) {',
     '        return (entrypoint.main as _UnaryFunction)(<String>[]);',

packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart

@@ -118,7 +118,7 @@ void main() {
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
 
     // Main
-    expect(generated, contains('ui.webOnlyWarmupEngine('));
+    expect(generated, contains('ui_web.bootstrapEngine('));
     expect(generated, contains('entrypoint.main as _'));
   }, overrides: <Type, Generator>{
     TemplateRenderer: () => const MustacheTemplateRenderer(),
@@ -270,7 +270,7 @@ void main() {
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
 
     // Main
-    expect(generated, contains('ui.webOnlyWarmupEngine('));
+    expect(generated, contains('ui_web.bootstrapEngine('));
     expect(generated, contains('entrypoint.main as _'));
   }, overrides: <Type, Generator>{
     Platform: () => windows,
@@ -295,7 +295,7 @@ void main() {
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
 
     // Main
-    expect(generated, contains('ui.webOnlyWarmupEngine('));
+    expect(generated, contains('ui_web.bootstrapEngine('));
     expect(generated, contains('entrypoint.main as _'));
   }, overrides: <Type, Generator>{
     TemplateRenderer: () => const MustacheTemplateRenderer(),
@@ -351,7 +351,7 @@ void main() {
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
 
     // Main
-    expect(generated, contains('ui.webOnlyWarmupEngine('));
+    expect(generated, contains('ui_web.bootstrapEngine('));
     expect(generated, contains('entrypoint.main as _'));
   }, overrides: <Type, Generator>{
     TemplateRenderer: () => const MustacheTemplateRenderer(),

packages/flutter_tools/test/general.shard/resident_web_runner_test.dart

@@ -730,8 +730,8 @@ void main() {
     final String entrypointContents =
         fileSystem.file(webDevFS.mainUri).readAsStringSync();
     expect(entrypointContents, contains('// Flutter web bootstrap script'));
-    expect(entrypointContents, contains("import 'dart:ui' as ui;"));
-    expect(entrypointContents, contains('await ui.webOnlyWarmupEngine('));
+    expect(entrypointContents, contains("import 'dart:ui_web' as ui_web;"));
+    expect(entrypointContents, contains('await ui_web.bootstrapEngine('));
 
     expect(logger.statusText, contains('Restarted application in'));
     expect(result.code, 0);

packages/flutter_web_plugins/lib/src/plugin_registry.dart

@@ -4,6 +4,7 @@
 
 import 'dart:async';
 import 'dart:ui' as ui;
+import 'dart:ui_web' as ui_web;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
@@ -57,13 +58,11 @@ class Registrar extends BinaryMessenger {
   /// previously-registered handler and replaces it with the handler
   /// from this object.
   ///
-  /// This method uses a function called `webOnlySetPluginHandler` in
-  /// the [dart:ui] library. That function is only available when
+  /// This method uses a function called `setPluginHandler` in
+  /// the [dart:ui_web] library. That function is only available when
   /// compiling for the web.
   void registerMessageHandler() {
-    // The `ui.webOnlySetPluginHandler` function below is only defined in the Web dart:ui.
-    // ignore: undefined_function, avoid_dynamic_calls
-    ui.webOnlySetPluginHandler(handleFrameworkMessage);
+    ui_web.setPluginHandler(handleFrameworkMessage);
   }
 
   /// Receives a platform message from the framework.
@@ -101,7 +100,7 @@ class Registrar extends BinaryMessenger {
   /// the following:
   ///
   /// ```dart
-  /// ui.webOnlySetPluginHandler(webPluginRegistrar.handleFrameworkMessage);
+  /// ui_web.setPluginHandler(handleFrameworkMessage);
   /// ```
   Future<void> handleFrameworkMessage(
     String channel,

packages/flutter_web_plugins/test/plugin_event_channel_test.dart

@@ -6,7 +6,7 @@
 library;
 
 import 'dart:async';
-import 'dart:ui' as ui;
+import 'dart:ui_web' as ui_web;
 
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -14,7 +14,7 @@ import 'package:flutter_web_plugins/flutter_web_plugins.dart';
 
 void main() {
   // Disabling tester emulation because this test relies on real message channel communication.
-  ui.debugEmulateFlutterTesterEnvironment = false; // ignore: undefined_prefixed_name
+  ui_web.debugEmulateFlutterTesterEnvironment = false;
 
   group('Plugin Event Channel', () {
     setUp(() {

packages/flutter_web_plugins/test/plugin_registry_test.dart

@@ -5,7 +5,7 @@
 @TestOn('chrome') // Uses web-only Flutter SDK
 library;
 
-import 'dart:ui' as ui;
+import 'dart:ui_web' as ui_web;
 
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -31,7 +31,7 @@ class TestPlugin {
 
 void main() {
   // Disabling tester emulation because this test relies on real message channel communication.
-  ui.debugEmulateFlutterTesterEnvironment = false; // ignore: undefined_prefixed_name
+  ui_web.debugEmulateFlutterTesterEnvironment = false;
 
   group('Plugin Registry', () {
     setUp(() {