DraggableScrollableController should dispatch creation in constructor. (#135423)

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

@@ -52,6 +52,13 @@ typedef ScrollableWidgetBuilder = Widget Function(
 /// fire when [pixels] changes without [size] changing. For example, if the
 /// constraints provided to an attached sheet change.
 class DraggableScrollableController extends ChangeNotifier {
+  /// Creates a controller for [DraggableScrollableSheet].
+  DraggableScrollableController() {
+    if (kFlutterMemoryAllocationsEnabled) {
+      ChangeNotifier.maybeDispatchObjectCreation(this);
+    }
+  }
+
   _DraggableScrollableSheetScrollController? _attachedController;
   final Set<AnimationController> _animationControllers = <AnimationController>{};
 

packages/flutter/test/material/scaffold_test.dart

@@ -273,6 +273,7 @@ void main() {
 
   testWidgetsWithLeakTracking('Floating action button shrinks when bottom sheet becomes dominant', (WidgetTester tester) async {
     final DraggableScrollableController draggableController = DraggableScrollableController();
+    addTearDown(draggableController.dispose);
     const double kBottomSheetDominatesPercentage = 0.3;
 
     await tester.pumpWidget(MaterialApp(home: Scaffold(
@@ -312,6 +313,7 @@ void main() {
 
   testWidgetsWithLeakTracking('Scaffold shows scrim when bottom sheet becomes dominant', (WidgetTester tester) async {
     final DraggableScrollableController draggableController = DraggableScrollableController();
+    addTearDown(draggableController.dispose);
     const double kBottomSheetDominatesPercentage = 0.3;
     const double kMinBottomSheetScrimOpacity = 0.1;
     const double kMaxBottomSheetScrimOpacity = 0.6;
@@ -2762,6 +2764,7 @@ void main() {
 
   testWidgetsWithLeakTracking('showBottomSheet removes scrim when draggable sheet is dismissed', (WidgetTester tester) async {
     final DraggableScrollableController draggableController = DraggableScrollableController();
+    addTearDown(draggableController.dispose);
     final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey();
     PersistentBottomSheetController<void>? sheetController;
 

packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart

@@ -1681,7 +1681,9 @@ void main() {
 
   testWidgetsWithLeakTracking('DraggableScrollableSheet controller can be changed while animating', (WidgetTester tester) async {
     final DraggableScrollableController controller1 = DraggableScrollableController();
+    addTearDown(controller1.dispose);
     final DraggableScrollableController controller2 = DraggableScrollableController();
+    addTearDown(controller2.dispose);
 
     DraggableScrollableController controller = controller1;
     await tester.pumpWidget(MaterialApp(
@@ -1733,4 +1735,11 @@ void main() {
     expect(controller1.isAttached, false);
     expect(controller2.isAttached, false);
   });
+
+  testWidgetsWithLeakTracking('$DraggableScrollableController dispatches creation in constructor.', (WidgetTester widgetTester) async {
+    await expectLater(
+      await memoryEvents(() async => DraggableScrollableController().dispose(), DraggableScrollableController),
+      areCreateAndDispose,
+    );
+  });
 }