Split Size into Size and Offset.

sky/engine/core/view/View.idl

 // 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.
 
 interface View {
   readonly attribute double devicePixelRatio;
+
+  // TODO(ianh): convert this to returning a Size
   readonly attribute double width;
   readonly attribute double height;
 
   attribute Picture picture;
 
   void setEventCallback(EventCallback callback);
   void setMetricsChangedCallback(VoidCallback callback);
 
   void setBeginFrameCallback(BeginFrameCallback callback);
   void scheduleFrame();
 };