Add:创建 flutter go web 版

packages/flutter_web/test/widgets/semantics_6_test.dart

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+// 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/material.dart';
+import 'package:flutter_web/rendering.dart';
+import 'package:flutter_web/widgets.dart';
+import 'package:flutter_web_test/flutter_web_test.dart';
+import 'package:meta/meta.dart';
+
+import 'semantics_tester.dart';
+
+void main() {
+  testWidgets('can change semantics in a branch blocked by BlockSemantics',
+      (WidgetTester tester) async {
+    final SemanticsTester semantics = SemanticsTester(tester);
+
+    final TestSemantics expectedSemantics = TestSemantics.root(
+      children: <TestSemantics>[
+        TestSemantics.rootChild(
+          id: 1,
+          label: 'hello',
+          textDirection: TextDirection.ltr,
+          rect: TestSemantics.fullScreen,
+        )
+      ],
+    );
+
+    await tester.pumpWidget(buildWidget(
+      blockedText: 'one',
+    ));
+
+    expect(semantics, hasSemantics(expectedSemantics));
+
+    // The purpose of the test is to ensure that this change does not throw.
+    await tester.pumpWidget(buildWidget(
+      blockedText: 'two',
+    ));
+
+    expect(semantics, hasSemantics(expectedSemantics));
+
+    // Ensure that the previously blocked semantics end up in the tree correctly when unblocked.
+    await tester.pumpWidget(buildWidget(
+      blockedText: 'two',
+      blocking: false,
+    ));
+    expect(semantics,
+        includesNodeWith(label: 'two', textDirection: TextDirection.ltr));
+
+    semantics.dispose();
+  });
+}
+
+Widget buildWidget({@required String blockedText, bool blocking = true}) {
+  assert(blockedText != null);
+  return Directionality(
+    textDirection: TextDirection.ltr,
+    child: Stack(fit: StackFit.expand, children: <Widget>[
+      Semantics(
+        container: true,
+        child: ListView(
+          children: <Widget>[
+            Text(blockedText),
+          ],
+        ),
+      ),
+      BlockSemantics(
+        blocking: blocking,
+        child: Semantics(
+          label: 'hello',
+          container: true,
+        ),
+      ),
+    ]),
+  );
+}