Use new dart:js_interop way to externalize/internalize objects (flutter#53304)

The issue in [0] was fixed. So we no longer have to use conditional
imports and dart2wasm vs dart2js specific implementations.

Instead we use the new extension methods introduced due to [0], namely
`Object.toExternalReference` and `ExternalDartReference.toDartObject`.

[0] dart-lang/sdk#55183

Author: mkustermann

ci/licenses_golden/licenses_flutter

@@ -40602,7 +40602,6 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/shadow.dart + ../../../flutte
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/canvas.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/codecs.dart + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/dart_js_conversion.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/filters.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/font_collection.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/image.dart + ../../../flutter/LICENSE
@@ -40639,7 +40638,6 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/shaders.da
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/surface.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/vertices.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_stub.dart + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_stub/dart_js_conversion.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_stub/renderer.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/svg.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/test_embedding.dart + ../../../flutter/LICENSE
@@ -43484,7 +43482,6 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/shadow.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/canvas.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/codecs.dart
-FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/dart_js_conversion.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/filters.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/font_collection.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/image.dart
@@ -43521,7 +43518,6 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/shaders.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/surface.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/vertices.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_stub.dart
-FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_stub/dart_js_conversion.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_stub/renderer.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/svg.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/test_embedding.dart

lib/web_ui/lib/src/engine/canvaskit/native_memory.dart

@@ -21,8 +21,8 @@ import 'package:ui/src/engine.dart';
 /// 5. The finalizer function is called with the SkPaint as the sole argument.
 /// 6. We call `delete` on SkPaint.
 DomFinalizationRegistry _finalizationRegistry = DomFinalizationRegistry(
-  (JSAny boxedUniq) {
-    final UniqueRef<Object> uniq = boxedUniq.fromJSWrapper as UniqueRef<Object>;
+  (ExternalDartReference boxedUniq) {
+    final UniqueRef<Object> uniq = boxedUniq.toDartObject as UniqueRef<Object>;
     uniq.collect();
   }.toJS
 );
@@ -34,7 +34,7 @@ NativeMemoryFinalizationRegistry nativeMemoryFinalizationRegistry = NativeMemory
 class NativeMemoryFinalizationRegistry {
   void register(Object owner, UniqueRef<Object> ref) {
     if (browserSupportsFinalizationRegistry) {
-      _finalizationRegistry.register(owner.toJSWrapper, ref.toJSWrapper);
+      _finalizationRegistry.register(owner.toExternalReference, ref.toExternalReference);
     }
   }
 }

lib/web_ui/lib/src/engine/dom.dart

@@ -9,7 +9,6 @@ import 'dart:typed_data';
 
 import 'package:js/js_util.dart' as js_util;
 import 'package:meta/meta.dart';
-import 'package:ui/src/engine/skwasm/skwasm_stub.dart' if (dart.library.ffi) 'package:ui/src/engine/skwasm/skwasm_impl.dart';
 
 import 'browser_detection.dart';
 
@@ -38,13 +37,6 @@ import 'browser_detection.dart';
 /// used carefully and only on types that are known to not contains `JSNull` and
 /// `JSUndefined`.
 extension ObjectToJSAnyExtension on Object {
-  // Once `Object.toJSBox` is faster (see
-  // https://github.com/dart-lang/sdk/issues/55183) we can remove this
-  // backend-specific workaround.
-  @pragma('wasm:prefer-inline')
-  @pragma('dart2js:tryInline')
-  JSAny get toJSWrapper => dartToJsWrapper(this);
-
   @pragma('wasm:prefer-inline')
   @pragma('dart2js:tryInline')
   JSAny get toJSAnyShallow {
@@ -61,10 +53,6 @@ extension ObjectToJSAnyExtension on Object {
 }
 
 extension JSAnyToObjectExtension on JSAny {
-  @pragma('wasm:prefer-inline')
-  @pragma('dart2js:tryInline')
-  Object get fromJSWrapper => jsWrapperToDart(this);
-
   @pragma('wasm:prefer-inline')
   @pragma('dart2js:tryInline')
   Object get toObjectShallow {
@@ -3674,13 +3662,14 @@ class DomFinalizationRegistry {
 
 extension DomFinalizationRegistryExtension on DomFinalizationRegistry {
   @JS('register')
-  external JSVoid register(JSAny target, JSAny value);
+  external JSVoid register(
+      ExternalDartReference target, ExternalDartReference value);
 
   @JS('register')
-  external JSVoid registerWithToken(JSAny target, JSAny value, JSAny token);
+  external JSVoid registerWithToken(ExternalDartReference target, ExternalDartReference value, ExternalDartReference token);
 
   @JS('unregister')
-  external JSVoid unregister(JSAny token);
+  external JSVoid unregister(ExternalDartReference token);
 }
 
 @JS('window.FinalizationRegistry')

lib/web_ui/lib/src/engine/skwasm/skwasm_impl.dart

@@ -11,7 +11,6 @@ import 'dart:ffi';
 
 export 'skwasm_impl/canvas.dart';
 export 'skwasm_impl/codecs.dart';
-export 'skwasm_impl/dart_js_conversion.dart';
 export 'skwasm_impl/filters.dart';
 export 'skwasm_impl/font_collection.dart';
 export 'skwasm_impl/image.dart';

lib/web_ui/lib/src/engine/skwasm/skwasm_impl/dart_js_conversion.dart

@@ -28,21 +28,21 @@ typedef DisposeFunction<T extends NativeType> = void Function(Pointer<T>);
 
 class SkwasmFinalizationRegistry<T extends NativeType> {
   SkwasmFinalizationRegistry(this.dispose)
-    : registry = DomFinalizationRegistry(((JSNumber address) =>
-      dispose(Pointer<T>.fromAddress(address.toDartDouble.toInt()))
+    : registry = DomFinalizationRegistry(((ExternalDartReference address) =>
+      dispose(Pointer<T>.fromAddress(address.toDartObject as int))
     ).toJS);
 
   final DomFinalizationRegistry registry;
   final DisposeFunction<T> dispose;
 
   void register(SkwasmObjectWrapper<T> wrapper) {
-    final JSAny jsWrapper = wrapper.toJSWrapper;
+    final ExternalDartReference jsWrapper = wrapper.toExternalReference;
     registry.registerWithToken(
-        jsWrapper, wrapper.handle.address.toJS, jsWrapper);
+        jsWrapper, wrapper.handle.address.toExternalReference, jsWrapper);
   }
 
   void evict(SkwasmObjectWrapper<T> wrapper) {
-    final JSAny jsWrapper = wrapper.toJSWrapper;
+    final ExternalDartReference jsWrapper = wrapper.toExternalReference;
     registry.unregister(jsWrapper);
     dispose(wrapper.handle);
   }

lib/web_ui/lib/src/engine/skwasm/skwasm_impl/memory.dart

@@ -6,5 +6,4 @@
 // ignore: unnecessary_library_directive
 library skwasm_stub;
 
-export 'skwasm_stub/dart_js_conversion.dart';
 export 'skwasm_stub/renderer.dart';

lib/web_ui/lib/src/engine/skwasm/skwasm_stub.dart

@@ -1929,7 +1929,7 @@ void _paragraphTests() {
     // So the test simply tests that a FinalizationRegistry can be constructed
     // and its `register` method can be called.
     final DomFinalizationRegistry registry = DomFinalizationRegistry((String arg) {}.toJS);
-    registry.register(Object().toJSWrapper, Object().toJSWrapper);
+    registry.register(Object().toExternalReference, Object().toExternalReference);
   });
 }