Roll engine to a031239a5d4e44e60d0ebc62b8c544a9f592fc22 (#14601)

Includes:
* Exclude frontend_server from the license crawl (https://github.com/flutter/engine/pull/4645)
* Make native wrapper classes non-abstract (https://github.com/flutter/engine/pull/4607)
* Restrict clang-format to C, C++, Obj-C, Obj-C++ (https://github.com/flutter/engine/pull/4654)

bin/internal/engine.version

-337764e4edebdafad6685a4af81b84d456dac687
+a031239a5d4e44e60d0ebc62b8c544a9f592fc22

packages/flutter/test/painting/decoration_test.dart

@@ -78,7 +78,7 @@ class DelayedImageProvider extends ImageProvider<DelayedImageProvider> {
   String toString() => '${describeIdentity(this)}}()';
 }
 
-class TestImage extends ui.Image {
+class TestImage implements ui.Image {
   @override
   int get width => 100;
 

packages/flutter/test/painting/fake_codec.dart

@@ -13,7 +13,7 @@ import 'package:flutter/foundation.dart';
 ///
 /// This is useful for running in the test Zone, where it is tricky to receive
 /// callbacks originating from the IO thread.
-class FakeCodec extends ui.Codec {
+class FakeCodec implements ui.Codec {
   final int _frameCount;
   final int _repetitionCount;
   final List<ui.FrameInfo> _frameInfos;
@@ -46,4 +46,7 @@ class FakeCodec extends ui.Codec {
     _nextFrame = (_nextFrame + 1) % _frameCount;
     return result;
   }
+
+  @override
+  void dispose() { }
 }

packages/flutter/test/painting/image_stream_test.dart

@@ -9,7 +9,7 @@ import 'package:flutter/painting.dart';
 import 'package:flutter/scheduler.dart' show timeDilation;
 import 'package:flutter_test/flutter_test.dart';
 
-class FakeFrameInfo extends FrameInfo {
+class FakeFrameInfo implements FrameInfo {
   final Duration _duration;
   final Image _image;
 
@@ -23,7 +23,7 @@ class FakeFrameInfo extends FrameInfo {
   Image get image => _image;
 }
 
-class FakeImage extends Image {
+class FakeImage implements Image {
   final int _width;
   final int _height;
 

packages/flutter/test/painting/shape_decoration_test.dart

@@ -112,7 +112,7 @@ class TestImageProvider extends ImageProvider<TestImageProvider> {
   }
 }
 
-class TestImage extends ui.Image {
+class TestImage implements ui.Image {
   @override
   int get width => 100;
 

packages/flutter/test/widgets/image_resolution_test.dart

@@ -12,7 +12,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-class TestImage extends ui.Image {
+class TestImage implements ui.Image {
   TestImage(this.scale);
   final double scale;
 

packages/flutter/test/widgets/image_rtl_test.dart

@@ -25,15 +25,15 @@ class TestImageProvider extends ImageProvider<TestImageProvider> {
   }
 }
 
-class TestImage extends ui.Image {
+class TestImage implements ui.Image {
   @override
   int get width => 16;
 
   @override
   int get height => 9;
 
-  // @override
-  // void dispose() { }
+  @override
+  void dispose() { }
 }
 
 void main() {

packages/flutter/test/widgets/image_test.dart

@@ -473,7 +473,7 @@ class TestImageStreamCompleter extends ImageStreamCompleter {
   }
 }
 
-class TestImage extends ui.Image {
+class TestImage implements ui.Image {
   @override
   int get width => 100;
 
@@ -482,4 +482,7 @@ class TestImage extends ui.Image {
 
   @override
   void dispose() { }
+
+  @override
+  String toString() => '[$width\u00D7$height]';
 }