TrainHoppingAnimation should dispatch creation and disposal events. (#141635)

packages/flutter/lib/src/animation/animations.dart

@@ -509,6 +509,15 @@ class TrainHoppingAnimation extends Animation<double>
     this._nextTrain, {
     this.onSwitchedTrain,
   }) {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      FlutterMemoryAllocations.instance.dispatchObjectCreated(
+        library: 'package:flutter/animation.dart',
+        className: '$TrainHoppingAnimation',
+        object: this,
+      );
+    }
     if (_nextTrain != null) {
       if (_currentTrain!.value == _nextTrain!.value) {
         _currentTrain = _nextTrain;
@@ -595,6 +604,11 @@ class TrainHoppingAnimation extends Animation<double>
   /// After this is called, this object is no longer usable.
   @override
   void dispose() {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      FlutterMemoryAllocations.instance.dispatchObjectDisposed(object: this);
+    }
     assert(_currentTrain != null);
     _currentTrain!.removeStatusListener(_statusChangeHandler);
     _currentTrain!.removeListener(_valueChangeHandler);

packages/flutter/test/animation/animations_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 import '../scheduler/scheduler_tester.dart';
 
@@ -127,6 +128,19 @@ void main() {
     expect(animation.toString(), contains('no next'));
   });
 
+  test('TrainHoppingAnimation dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => TrainHoppingAnimation(
+          const AlwaysStoppedAnimation<double>(1),
+          const AlwaysStoppedAnimation<double>(1),
+        ).dispose(),
+        TrainHoppingAnimation,
+      ),
+      areCreateAndDispose,
+    );
+  });
+
   test('AnimationMean control test', () {
     final AnimationController left = AnimationController(
       value: 0.5,