MultiDragPointerState should dispatch creation and disposal events. (#138807)

packages/flutter/lib/src/gestures/multidrag.dart

@@ -33,7 +33,17 @@ typedef GestureMultiDragStartCallback = Drag? Function(Offset position);
 abstract class MultiDragPointerState {
   /// Creates per-pointer state for a [MultiDragGestureRecognizer].
   MultiDragPointerState(this.initialPosition, this.kind, this.gestureSettings)
-    : _velocityTracker = VelocityTracker.withKind(kind);
+    : _velocityTracker = VelocityTracker.withKind(kind) {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      MemoryAllocations.instance.dispatchObjectCreated(
+        library: 'package:flutter/gestures.dart',
+        className: '$MultiDragPointerState',
+        object: this,
+      );
+    }
+  }
 
   /// Device specific gesture configuration that should be preferred over
   /// framework constants.
@@ -178,6 +188,11 @@ abstract class MultiDragPointerState {
   @protected
   @mustCallSuper
   void dispose() {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      MemoryAllocations.instance.dispatchObjectDisposed(object: this);
+    }
     _arenaEntry?.resolve(GestureDisposition.rejected);
     _arenaEntry = null;
     assert(() {

packages/flutter/test/gestures/multidrag_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:flutter/gestures.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 import 'gesture_tester.dart';
 
@@ -111,4 +112,34 @@ void main() {
     // ignore: invalid_use_of_protected_member
     expect(recognizer2.isPointerAllowed(rejectedPointer), false);
   });
+
+  test('$MultiDragPointerState dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => _MultiDragPointerState(
+          Offset.zero,
+          PointerDeviceKind.touch,
+          null,
+        ).dispose(),
+        _MultiDragPointerState,
+      ),
+      areCreateAndDispose,
+    );
+  });
+}
+
+class _MultiDragPointerState extends MultiDragPointerState {
+  _MultiDragPointerState(
+    super.initialPosition,
+    super.kind,
+    super.gestureSettings,
+  );
+
+  @override
+  void accepted(GestureMultiDragStartCallback starter) {}
+
+  @override
+  void dispose() {
+    super.dispose();
+  }
 }