AppLifecycleListener should dispatch creation and disposal events. (#137840)

Author: ksokolovskyi

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

@@ -73,6 +73,15 @@ class AppLifecycleListener with WidgetsBindingObserver, Diagnosticable {
     this.onStateChange,
   })  : binding = binding ?? WidgetsBinding.instance,
         _lifecycleState = (binding ?? WidgetsBinding.instance).lifecycleState {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      MemoryAllocations.instance.dispatchObjectCreated(
+        library: 'package:flutter/widgets.dart',
+        className: '$AppLifecycleListener',
+        object: this,
+      );
+    }
     this.binding.addObserver(this);
   }
 
@@ -174,6 +183,11 @@ class AppLifecycleListener with WidgetsBindingObserver, Diagnosticable {
   @mustCallSuper
   void dispose() {
     assert(_debugAssertNotDisposed());
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      MemoryAllocations.instance.dispatchObjectDisposed(object: this);
+    }
     binding.removeObserver(this);
     assert(() {
       _debugDisposed = true;

packages/flutter/test/widgets/app_lifecycle_listener_test.dart

@@ -10,7 +10,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 void main() {
-  late AppLifecycleListener listener;
+  AppLifecycleListener? listener;
 
   Future<void> setAppLifeCycleState(AppLifecycleState state) async {
     final ByteData? message = const StringCodec().encodeMessage(state.toString());
@@ -40,7 +40,8 @@ void main() {
   });
 
   tearDown(() {
-    listener.dispose();
+    listener?.dispose();
+    listener = null;
     final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.instance;
     binding.resetLifecycleState();
     binding.platformDispatcher.resetInitialLifecycleState();
@@ -163,6 +164,16 @@ void main() {
     await sendAppExitRequest();
     expect(exitRequested, isTrue);
   });
+
+  test('AppLifecycleListener dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => AppLifecycleListener(binding: WidgetsBinding.instance).dispose(),
+        AppLifecycleListener,
+      ),
+      areCreateAndDispose,
+    );
+  });
 }
 
 class TestAppLifecycleListener extends AppLifecycleListener {