Add:创建 flutter go web 版

packages/flutter_web/test/rendering/dynamic_intrinsics_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/rendering.dart';
+import '../flutter_test_alternative.dart';
+
+import 'rendering_tester.dart';
+
+class RenderFixedSize extends RenderBox {
+  double dimension = 100.0;
+
+  void grow() {
+    dimension *= 2.0;
+    markNeedsLayout();
+  }
+
+  @override
+  double computeMinIntrinsicWidth(double height) => dimension;
+  @override
+  double computeMaxIntrinsicWidth(double height) => dimension;
+  @override
+  double computeMinIntrinsicHeight(double width) => dimension;
+  @override
+  double computeMaxIntrinsicHeight(double width) => dimension;
+
+  @override
+  void performLayout() {
+    size = Size.square(dimension);
+  }
+}
+
+class RenderParentSize extends RenderProxyBox {
+  RenderParentSize({RenderBox child}) : super(child);
+
+  @override
+  bool get sizedByParent => true;
+
+  @override
+  void performResize() {
+    size = constraints.biggest;
+  }
+
+  @override
+  void performLayout() {
+    child.layout(constraints);
+  }
+}
+
+class RenderIntrinsicSize extends RenderProxyBox {
+  RenderIntrinsicSize({RenderBox child}) : super(child);
+
+  @override
+  void performLayout() {
+    child.layout(constraints);
+    size = Size(child.getMinIntrinsicWidth(double.infinity),
+        child.getMinIntrinsicHeight(double.infinity));
+  }
+}
+
+void main() {
+  test('Whether using intrinsics means you get hooked into layout', () {
+    RenderBox root;
+    RenderFixedSize inner;
+    layout(
+        root = RenderIntrinsicSize(
+            child: RenderParentSize(child: inner = RenderFixedSize())),
+        constraints: const BoxConstraints(
+            minWidth: 0.0,
+            minHeight: 0.0,
+            maxWidth: 1000.0,
+            maxHeight: 1000.0));
+    expect(root.size, equals(inner.size));
+
+    inner.grow();
+    pumpFrame();
+    expect(root.size, equals(inner.size));
+  });
+}