Add:创建 flutter go web 版

packages/flutter_web/test/widgets/annotated_region_test.dart

@@ -0,0 +1,23 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_web/rendering.dart';
+import 'package:flutter_web/widgets.dart';
+import 'package:flutter_web_test/flutter_web_test.dart';
+
+void main() {
+  testWidgets('provides a value to the layer tree',
+      (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const AnnotatedRegion<int>(
+        child: SizedBox(width: 100.0, height: 100.0),
+        value: 1,
+      ),
+    );
+    final List<Layer> layers = tester.layers;
+    final AnnotatedRegionLayer<int> layer =
+        layers.firstWhere((Layer layer) => layer is AnnotatedRegionLayer<int>);
+    expect(layer.value, 1);
+  });
+}