Don't use a factory constructor on the finalization registry.

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

@@ -20,7 +20,7 @@ import 'package:ui/src/engine.dart';
 /// 4. GC decides to perform a GC cycle and collects CkPaint.
 /// 5. The finalizer function is called with the SkPaint as the sole argument.
 /// 6. We call `delete` on SkPaint.
-DomFinalizationRegistry _finalizationRegistry = DomFinalizationRegistry(
+DomFinalizationRegistry _finalizationRegistry = createDomFinalizationRegistry(
   (UniqueRef<Object> uniq) {
     uniq.collect();
   }.toJS

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

@@ -3438,9 +3438,19 @@ extension DomTextDecoderExtension on DomTextDecoder {
 
 @JS('window.FinalizationRegistry')
 @staticInterop
-class DomFinalizationRegistry {
-  external factory DomFinalizationRegistry(JSFunction cleanup);
-}
+class DomFinalizationRegistry {}
+
+@JS('window.FinalizationRegistry')
+external JSAny? get _finalizationRegistryConstructor;
+
+// Note: We don't use a factory constructor here because there is an issue in
+// dart2js that causes a crash in the Google3 build if we do use a factory
+// constructor. See b/284478971
+DomFinalizationRegistry createDomFinalizationRegistry(JSFunction cleanup) =>
+  js_util.callConstructor(
+    _finalizationRegistryConstructor!.toObjectShallow,
+    <Object>[cleanup]
+  );
 
 extension DomFinalizationRegistryExtension on DomFinalizationRegistry {
   @JS('register')
@@ -3461,9 +3471,6 @@ extension DomFinalizationRegistryExtension on DomFinalizationRegistry {
   void unregister(Object token) => _unregister(token.toJSAnyShallow);
 }
 
-@JS('window.FinalizationRegistry')
-external JSAny? get _finalizationRegistryConstructor;
-
 /// Whether the current browser supports `FinalizationRegistry`.
 bool browserSupportsFinalizationRegistry =
     _finalizationRegistryConstructor != null;

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

@@ -28,7 +28,7 @@ typedef DisposeFunction<T extends NativeType> = void Function(Pointer<T>);
 
 class SkwasmFinalizationRegistry<T extends NativeType> {
   SkwasmFinalizationRegistry(this.dispose)
-    : registry = DomFinalizationRegistry(((JSNumber address) =>
+    : registry = createDomFinalizationRegistry(((JSNumber address) =>
       dispose(Pointer<T>.fromAddress(address.toDart.toInt()))
     ).toJS);
 

lib/web_ui/test/canvaskit/canvaskit_api_test.dart

@@ -1907,7 +1907,7 @@ void _paragraphTests() {
     // FinalizationRegistry because it depends on GC, which cannot be controlled,
     // 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);
+    final DomFinalizationRegistry registry = createDomFinalizationRegistry((String arg) {}.toJS);
     registry.register(Object(), Object());
   });
 }