(Test-only) Add tests for new ImageFilter.dilate/ImageFilter.erode in flutter engine (#101036)

Author: fzyzcjy

packages/flutter/test/widgets/image_filter_test.dart

@@ -9,6 +9,7 @@
 import 'dart:typed_data';
 import 'dart:ui';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -29,6 +30,37 @@ void main() {
     );
   });
 
+  testWidgets('Image filter - dilate', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      RepaintBoundary(
+        child: ImageFiltered(
+          imageFilter: ImageFilter.dilate(radiusX: 10.0, radiusY: 10.0),
+          child: const Placeholder(),
+        ),
+      ),
+    );
+    await expectLater(
+      find.byType(ImageFiltered),
+      matchesGoldenFile('image_filter_dilate.png'),
+    );
+  }, skip: kIsWeb); // https://github.com/flutter/flutter/issues/101874
+
+  testWidgets('Image filter - erode', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      RepaintBoundary(
+        child: ImageFiltered(
+          // Do not erode too much, otherwise we will see nothing left.
+          imageFilter: ImageFilter.erode(radiusX: 1.0, radiusY: 1.0),
+          child: const Placeholder(strokeWidth: 4),
+        ),
+      ),
+    );
+    await expectLater(
+      find.byType(ImageFiltered),
+      matchesGoldenFile('image_filter_erode.png'),
+    );
+  }, skip: kIsWeb); // https://github.com/flutter/flutter/issues/101874
+
   testWidgets('Image filter - matrix', (WidgetTester tester) async {
     final ImageFilter matrix = ImageFilter.matrix(Float64List.fromList(<double>[
       0.5, 0.0, 0.0, 0.0, //