BannerPainter should dispatch creation and disposal events. (#137472)

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

@@ -23,6 +23,8 @@ const TextStyle _kTextStyle = TextStyle(
   height: 1.0,
 );
 
+const String _flutterWidgetsLibrary = 'package:flutter/widgets.dart';
+
 /// Where to show a [Banner].
 ///
 /// The start and end locations are relative to the ambient [Directionality]
@@ -61,7 +63,17 @@ class BannerPainter extends CustomPainter {
     required this.layoutDirection,
     this.color = _kColor,
     this.textStyle = _kTextStyle,
-  }) : super(repaint: PaintingBinding.instance.systemFonts);
+  }) : super(repaint: PaintingBinding.instance.systemFonts) {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      MemoryAllocations.instance.dispatchObjectCreated(
+        library: _flutterWidgetsLibrary,
+        className: '$BannerPainter',
+        object: this,
+      );
+    }
+  }
 
   /// The message to show in the banner.
   final String message;
@@ -117,6 +129,11 @@ class BannerPainter extends CustomPainter {
   ///
   /// After calling this method, this object is no longer usable.
   void dispose() {
+    // TODO(polina-c): stop duplicating code across disposables
+    // https://github.com/flutter/flutter/issues/137435
+    if (kFlutterMemoryAllocationsEnabled) {
+      MemoryAllocations.instance.dispatchObjectDisposed(object: this);
+    }
     _textPainter?.dispose();
     _textPainter = null;
   }

packages/flutter/test/widgets/banner_test.dart

@@ -280,4 +280,19 @@ void main() {
     );
     debugDisableShadows = true;
   });
+
+  test('BannerPainter dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => BannerPainter(
+          message: 'foo',
+          textDirection: TextDirection.rtl,
+          location: BannerLocation.topStart,
+          layoutDirection: TextDirection.ltr,
+        ).dispose(),
+        BannerPainter,
+      ),
+      areCreateAndDispose,
+    );
+  });
 }