Add:创建 flutter go web 版

packages/flutter_web/test/rendering/overflow_test.dart

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+// Copyright 2015 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 '../flutter_test_alternative.dart';
+
+import 'rendering_tester.dart';
+
+void main() {
+  test('overflow should not affect baseline', () {
+    RenderBox root, child, text;
+    double baseline1, baseline2, height1, height2;
+
+    root = RenderPositionedBox(
+      child: RenderCustomPaint(
+        child: child = text = RenderParagraph(
+          const TextSpan(text: 'Hello World'),
+          textDirection: TextDirection.ltr,
+        ),
+        painter: TestCallbackPainter(
+          onPaint: () {
+            baseline1 = child.getDistanceToBaseline(TextBaseline.alphabetic);
+            height1 = text.size.height;
+          },
+        ),
+      ),
+    );
+    layout(root, phase: EnginePhase.paint);
+
+    root = RenderPositionedBox(
+      child: RenderCustomPaint(
+        child: child = RenderConstrainedOverflowBox(
+          child: text = RenderParagraph(
+            const TextSpan(text: 'Hello World'),
+            textDirection: TextDirection.ltr,
+          ),
+          maxHeight: height1 / 2.0,
+          alignment: Alignment.topLeft,
+        ),
+        painter: TestCallbackPainter(
+          onPaint: () {
+            baseline2 = child.getDistanceToBaseline(TextBaseline.alphabetic);
+            height2 = text.size.height;
+          },
+        ),
+      ),
+    );
+    layout(root, phase: EnginePhase.paint);
+
+    expect(baseline1, lessThan(height1));
+    expect(height2, equals(height1 / 2.0));
+    expect(baseline2, equals(baseline1));
+    expect(baseline2, greaterThan(height2));
+  });
+}