[Ash] Copy alpha_shape when recreating layers.

ui/compositor/layer.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 185 matching lines @@
 
   // Return the target grayscale if animator is running, or the current
   // grayscale otherwise.
   float GetTargetGrayscale() const;
 
   // Zoom the background by a factor of |zoom|. The effect is blended along the
   // edge across |inset| pixels.
   void SetBackgroundZoom(float zoom, int inset);
 
   // Set the shape of this layer.
+  SkRegion* alpha_shape() const { return alpha_shape_.get(); }
   void SetAlphaShape(scoped_ptr<SkRegion> region);
 
   // Invert the layer.
   bool layer_inverted() const { return layer_inverted_; }
   void SetLayerInverted(bool inverted);
 
   // Return the target opacity if animator is running, or the current opacity
   // otherwise.
   float GetTargetOpacity() const;
 
@@ skipping 296 matching lines @@
   // The size of the frame or texture in DIP, set when SetShowDelegatedContent
   // or SetTextureMailbox was called.
   gfx::Size frame_size_in_dip_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_