Revert "Fix custom Elements that wants to decorate State.build (#49925)" (#50068)

This reverts commit a1143d17.

packages/flutter/lib/src/widgets/framework.dart

@@ -4586,7 +4586,13 @@ class StatefulElement extends ComponentElement {
   }
 
   @override
-  Widget build() => _state.build(this);
+  Widget build() {
+    if (_didChangeDependencies) {
+      _state.didChangeDependencies();
+      _didChangeDependencies = false;
+    }
+    return state.build(this);
+  }
 
   /// The [State] instance associated with this location in the tree.
   ///
@@ -4636,15 +4642,6 @@ class StatefulElement extends ComponentElement {
     super._firstBuild();
   }
 
-  @override
-  void performRebuild() {
-    if (_didChangeDependencies) {
-      _state.didChangeDependencies();
-      _didChangeDependencies = false;
-    }
-    super.performRebuild();
-  }
-
   @override
   void update(StatefulWidget newWidget) {
     super.update(newWidget);

packages/flutter/test/widgets/framework_test.dart

@@ -1259,80 +1259,6 @@ void main() {
     expect(state.didChangeDependenciesCount, 3);
     expect(state.deactivatedCount, 2);
   });
-
-  testWidgets('StatefulElement subclass can decorate State.build', (WidgetTester tester) async {
-    bool isDidChangeDependenciesDecorated;
-    bool isBuildDecorated;
-
-    final Widget child = Decorate(
-      didChangeDependencies: (bool value) {
-        isDidChangeDependenciesDecorated = value;
-      },
-      build: (bool value) {
-        isBuildDecorated = value;
-      }
-    );
-
-    await tester.pumpWidget(Inherited(0, child: child));
-
-    expect(isBuildDecorated, isTrue);
-    expect(isDidChangeDependenciesDecorated, isFalse);
-
-    await tester.pumpWidget(Inherited(1, child: child));
-
-    expect(isBuildDecorated, isTrue);
-    expect(isDidChangeDependenciesDecorated, isFalse);
-  });
-}
-
-class Decorate extends StatefulWidget {
-  const Decorate({
-    Key key,
-    @required this.didChangeDependencies,
-    @required this.build
-  }) :
-    assert(didChangeDependencies != null),
-    assert(build != null),
-    super(key: key);
-
-  final void Function(bool isInBuild) didChangeDependencies;
-  final void Function(bool isInBuild) build;
-
-  @override
-  _DecorateState createState() => _DecorateState();
-
-  @override
-  DecorateElement createElement() => DecorateElement(this);
-}
-
-class DecorateElement extends StatefulElement {
-  DecorateElement(Decorate widget): super(widget);
-
-  bool isDecorated = false;
-
-  @override
-  Widget build() {
-    try {
-      isDecorated = true;
-      return super.build();
-    } finally {
-      isDecorated = false;
-    }
-  }
-}
-
-class _DecorateState extends State<Decorate> {
-  @override
-  void didChangeDependencies() {
-    super.didChangeDependencies();
-    widget.didChangeDependencies.call((context as DecorateElement).isDecorated);
-  }
-  @override
-  Widget build(covariant DecorateElement context) {
-    context.dependOnInheritedWidgetOfExactType<Inherited>();
-    widget.build.call(context.isDecorated);
-    return Container();
-  }
 }
 
 class NullChildTest extends Widget {