Replace BoxDimensions with sky.Size

sky/tests/raw/render_flex.dart

 // 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 '../resources/third_party/unittest/unittest.dart';
 import '../resources/unit.dart';
 import 'dart:sky' as sky;
 import 'package:sky/framework/app.dart';
 import 'package:sky/framework/layout2.dart';
 
 class RenderSolidColor extends RenderDecoratedBox {
   final sky.Size desiredSize;
   final int backgroundColor;
 
   RenderSolidColor(int backgroundColor, { this.desiredSize: const sky.Size.infinite() })
       : backgroundColor = backgroundColor,
         super(new BoxDecoration(backgroundColor: backgroundColor)) {
   }
 
-  BoxDimensions getIntrinsicDimensions(BoxConstraints constraints) {
-    return new BoxDimensions.withConstraints(constraints,
-                                             width: desiredSize.width,
-                                             height: desiredSize.height);
+  sky.Size getIntrinsicDimensions(BoxConstraints constraints) {
+    return constraints.constrain(desiredSize);
   }
 
   void performLayout() {
     size = constraints.constrain(desiredSize);
   }
 
   void handlePointer(sky.PointerEvent event) {
     if (event.type == 'pointerdown')
       decoration = new BoxDecoration(backgroundColor: 0xFFFF0000);
     else if (event.type == 'pointerup')
@@ skipping 42 matching lines @@
     root.add(row);
     row.parentData.flex = 3;
 
     app = new AppView(root);
 
     expect(root.size.width, equals(sky.view.width));
     expect(root.size.height, equals(sky.view.height));
     expect(renderBlock.size.width, equals(sky.view.width - 20.0));
   });
 }