Split Size into Size and Offset.

sky/engine/core/painting/DrawLooperLayerInfo.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.
 
 [
   Constructor(),
 ] interface DrawLooperLayerInfo {
   // Specifies which aspects of the layer's paint should replace the
   // corresponding aspects on the draw's paint. Use PaintBits, defined in
   // DrawLooperLayerInfo.dart.
   void setPaintBits(unsigned long bits);
   void setColorMode(TransferMode mode);
-  // TODO(eseidel): Offset should be a Size not a Point.
-  void setOffset(Point offset);
+  void setOffset(Offset offset);
   void setPostTranslate(boolean postTranslate);
 };