Allow WebExternalTextureLayerClient to work with mailboxes.

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 289 matching lines @@
   // ContentLayerClient
   virtual void PaintContents(
       SkCanvas* canvas, gfx::Rect clip, gfx::RectF* opaque) OVERRIDE;
   virtual void DidChangeLayerCanUseLCDText() OVERRIDE {}
 
   cc::Layer* cc_layer() { return cc_layer_; }
 
   // TextureLayerClient
   virtual unsigned PrepareTexture(cc::ResourceUpdateQueue* queue) OVERRIDE;
   virtual WebKit::WebGraphicsContext3D* Context3d() OVERRIDE;
+  virtual bool PrepareTextureMailbox(cc::TextureMailbox*) OVERRIDE;
 
   float device_scale_factor() const { return device_scale_factor_; }
 
   // Forces a render surface to be used on this layer. This has no positive
   // impact, and is only used for benchmarking/testing purpose.
   void SetForceRenderSurface(bool force);
   bool force_render_surface() const { return force_render_surface_; }
 
   // LayerAnimationEventObserver
   virtual void OnAnimationStarted(const cc::AnimationEvent& event) OVERRIDE;
@@ skipping 147 matching lines @@
   // The size of the delegated frame in DIP, set when SetDelegatedFrame was
   // called.
   gfx::Size delegated_frame_size_in_dip_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_