Make RenderWidgetHostViewAura::CopyFromCompositingSurface readback layer

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 5aa6a96a8e7cbf9b71ee3a466b69f4f94e2b988b..b5316216e6305331b63935fc94ee737df1c2cc59 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -500,6 +500,7 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
 
   void ComputeTouchLatency(const ui::LatencyInfo& latency_info);
   void FrameSwapped(const ui::LatencyInfo& latency_info);
+  void DidReceiveRendererFrame();
 
   // Returns the ID that uniquely describes this component to the latency
   // subsystem.
@@ -633,8 +634,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   void OnSetTooltipText(const string16& tooltip_text,
                         WebKit::WebTextDirection text_direction_hint);
   void OnPaintAtSizeAck(int tag, const gfx::Size& size);
+#if defined(OS_MACOSX)
   void OnCompositorSurfaceBuffersSwapped(
       const ViewHostMsg_CompositorSurfaceBuffersSwapped_Params& params);
+#endif
   bool OnSwapCompositorFrame(const IPC::Message& message);
   void OnOverscrolled(gfx::Vector2dF accumulated_overscroll,
                       gfx::Vector2dF current_fling_velocity);