SnapshotPainter should dispatch creation and disposal events. (#138810)

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

@@ -4,6 +4,7 @@
 
 import 'dart:ui' as ui;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';
@@ -385,7 +386,14 @@ class _RenderSnapshotWidget extends RenderProxyBox {
 /// }
 /// ```
 /// {@end-tool}
-abstract class SnapshotPainter extends ChangeNotifier  {
+abstract class SnapshotPainter extends ChangeNotifier {
+  /// Creates an instance of [SnapshotPainter].
+  SnapshotPainter() {
+    if (kFlutterMemoryAllocationsEnabled) {
+      ChangeNotifier.maybeDispatchObjectCreation(this);
+    }
+  }
+
   /// Called whenever the [image] that represents a [SnapshotWidget]s child should be painted.
   ///
   /// The image is rasterized at the physical pixel resolution and should be scaled down by

packages/flutter/test/widgets/snapshot_widget_test.dart

@@ -326,6 +326,16 @@ void main() {
     await expectLater(find.byKey(repaintBoundaryKey), matchesReferenceImage(imageWhenDisabled));
   },
   skip: kIsWeb); // TODO(jonahwilliams): https://github.com/flutter/flutter/issues/106689
+
+  test('SnapshotPainter dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => TestPainter().dispose(),
+        TestPainter,
+      ),
+      areCreateAndDispose,
+    );
+  });
 }
 
 class TestPlatformView extends SingleChildRenderObjectWidget {