Re-land "Add a Color class to dart:sky."

sky/sdk/lib/framework/rendering/render_box.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 'render_node.dart';
 import 'dart:sky' as sky;
 
 // GENERIC BOX RENDERING
 // Anything that has a concept of x, y, width, height is going to derive from this
 
@@ skipping 202 matching lines @@
         child.hitTest(result, position: new sky.Point(position.x - child.parentData.position.x,
                                                       position.y - child.parentData.position.y));
       }
     }
   }
 
 }
 
 // This must be immutable, because we won't notice when it changes
 class BoxDecoration {
-  const BoxDecoration({
-    this.backgroundColor
-  });
+  // TODO(mpcomplete): go through and change the users of this class to pass
+  // a Color object.
+  BoxDecoration({
+    backgroundColor
+  }) : backgroundColor = new sky.Color(backgroundColor);
 
-  final int backgroundColor;
+  final sky.Color backgroundColor;
 }
 
 class RenderDecoratedBox extends RenderProxyBox {
 
   RenderDecoratedBox({
     BoxDecoration decoration,
     RenderBox child
   }) : _decoration = decoration, super(child);
 
   BoxDecoration _decoration;
@@ skipping 122 matching lines @@
 
   void defaultPaint(RenderNodeDisplayList canvas) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position);
       child = child.parentData.nextSibling;
     }
   }
 }