Test cover painting for memory leaks (#136696)

packages/flutter/test/painting/decoration_image_lerp_test.dart

@@ -14,9 +14,10 @@ import 'dart:ui' as ui;
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 void main() {
-  testWidgets('ImageDecoration.lerp', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('ImageDecoration.lerp', (WidgetTester tester) async {
     final MemoryImage green = MemoryImage(Uint8List.fromList(<int>[
       0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,  0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
       0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01,  0x01, 0x03, 0x00, 0x00, 0x00, 0x25, 0xdb, 0x56,
@@ -159,6 +160,7 @@ void main() {
 
     if (!kIsWeb) { // TODO(ianh): https://github.com/flutter/flutter/issues/130610
       final ui.Image image = (await tester.binding.runAsync<ui.Image>(() => captureImage(find.byType(Wrap).evaluate().single)))!;
+      addTearDown(() => image.dispose());
       final Uint8List bytes = (await tester.binding.runAsync<ByteData?>(() => image.toByteData(format: ui.ImageByteFormat.rawStraightRgba)))!.buffer.asUint8List();
       expect(image.width, 792);
       expect(image.height, 48);
@@ -189,7 +191,7 @@ void main() {
     }
   }, skip: kIsWeb); // TODO(ianh): https://github.com/flutter/flutter/issues/130612, https://github.com/flutter/flutter/issues/130609
 
-  testWidgets('ImageDecoration.lerp', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('ImageDecoration.lerp', (WidgetTester tester) async {
     final MemoryImage cmyk = MemoryImage(Uint8List.fromList(<int>[
       0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,  0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
       0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x04,  0x02, 0x03, 0x00, 0x00, 0x00, 0xd4, 0x9f, 0x76,
@@ -355,6 +357,7 @@ void main() {
 
     if (!kIsWeb) { // TODO(ianh): https://github.com/flutter/flutter/issues/130610
       final ui.Image image = (await tester.binding.runAsync<ui.Image>(() => captureImage(find.byType(Wrap).evaluate().single)))!;
+      addTearDown(() => image.dispose());
       final Uint8List bytes = (await tester.binding.runAsync<ByteData?>(() => image.toByteData(format: ui.ImageByteFormat.rawStraightRgba)))!.buffer.asUint8List();
       expect(image.width, 24 * 24);
       expect(image.height, 1 * 24);
@@ -406,7 +409,7 @@ void main() {
     }
   }, skip: kIsWeb); // TODO(ianh): https://github.com/flutter/flutter/issues/130612, https://github.com/flutter/flutter/issues/130609
 
-  testWidgets('ImageDecoration.lerp with colored background', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('ImageDecoration.lerp with colored background', (WidgetTester tester) async {
     final MemoryImage cmyk = MemoryImage(Uint8List.fromList(<int>[
       0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,  0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
       0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x04,  0x02, 0x03, 0x00, 0x00, 0x00, 0xd4, 0x9f, 0x76,

packages/flutter/test/painting/gradient_test.dart

@@ -11,6 +11,7 @@ import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 void main() {
   test('LinearGradient scale test', () {
@@ -881,7 +882,7 @@ void main() {
 
     group('Gradients - 45 degrees', () {
       for (final Gradient gradient in gradients45) {
-        testWidgets('$gradient', (WidgetTester tester) async {
+        testWidgetsWithLeakTracking('$gradient', (WidgetTester tester) async {
           await runTest(tester, gradient, 45);
         });
       }
@@ -889,7 +890,7 @@ void main() {
 
     group('Gradients - 90 degrees', () {
       for (final Gradient gradient in gradients90) {
-        testWidgets('$gradient', (WidgetTester tester) async {
+        testWidgetsWithLeakTracking('$gradient', (WidgetTester tester) async {
           await runTest(tester, gradient, 90);
         });
       }