Make reftests work for sky.

sky/compositor/layer.h

 // Copyright 2014 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 SKY_COMPOSITOR_LAYER_H_
 #define SKY_COMPOSITOR_LAYER_H_
 
 #include "base/memory/ref_counted.h"
 #include "mojo/gpu/gl_texture.h"
 #include "sky/compositor/layer_client.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace sky {
+
+class DisplayDelegate;
 class LayerHost;
 
 class Layer : public base::RefCounted<Layer> {
  public:
   explicit Layer(LayerClient* client);
 
-  void ClearClient();
-
   void SetSize(const gfx::Size& size);
+  void GetPixelsForTesting(std::vector<unsigned char>* pixels);
   void Display();
 
   scoped_ptr<mojo::GLTexture> GetTexture();
 
   const gfx::Size& size() const { return size_; }
 
   void set_host(LayerHost* host) { host_ = host; }
 
  private:
   friend class base::RefCounted<Layer>;
   ~Layer();
 
   LayerClient* client_;
   LayerHost* host_;
   gfx::Size size_;
-
   scoped_ptr<mojo::GLTexture> texture_;
+  scoped_ptr<DisplayDelegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace sky
 
 #endif  // SKY_COMPOSITOR_LAYER_H_