Add:创建 flutter go web 版

packages/flutter_web/test/semantics/semantics_service_test.dart

@@ -0,0 +1,43 @@
+// Copyright 2017 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_ui/ui.dart' show TextDirection;
+
+import 'package:flutter_web/semantics.dart';
+import 'package:flutter_web/services.dart' show SystemChannels;
+import 'package:test/test.dart';
+
+void main() {
+  test('Semantic announcement', () async {
+    final List<Map<dynamic, dynamic>> log = <Map<dynamic, dynamic>>[];
+
+    SystemChannels.accessibility
+        .setMockMessageHandler((Object mockMessage) async {
+      final Map<dynamic, dynamic> message = mockMessage;
+      log.add(message);
+    });
+
+    await SemanticsService.announce('announcement 1', TextDirection.ltr);
+    await SemanticsService.announce('announcement 2', TextDirection.rtl);
+
+    expect(
+        log,
+        equals(<Map<String, dynamic>>[
+          <String, dynamic>{
+            'type': 'announce',
+            'data': <String, dynamic>{
+              'message': 'announcement 1',
+              'textDirection': 1
+            }
+          },
+          <String, dynamic>{
+            'type': 'announce',
+            'data': <String, dynamic>{
+              'message': 'announcement 2',
+              'textDirection': 0
+            }
+          },
+        ]));
+  });
+}