Clean up GPU back-pressure with remote CALayers

content/common/gpu/image_transport_surface.h

Index: content/common/gpu/image_transport_surface.h
diff --git a/content/common/gpu/image_transport_surface.h b/content/common/gpu/image_transport_surface.h
index 19f6881b05fd0aa41b033f84a60da0f0fe97cbde..9d9fa63f2304ac14506a6e4cd85732e94d44d3a1 100644
--- a/content/common/gpu/image_transport_surface.h
+++ b/content/common/gpu/image_transport_surface.h
@@ -57,8 +57,10 @@ class ImageTransportSurface {
  public:
   ImageTransportSurface();
 
+#if defined(OS_MACOSX)
   virtual void OnBufferPresented(
       const AcceleratedSurfaceMsg_BufferPresented_Params& params) = 0;
+#endif
   virtual void OnResize(gfx::Size size, float scale_factor) = 0;
   virtual void SetLatencyInfo(
       const std::vector<ui::LatencyInfo>& latency_info) = 0;
@@ -142,8 +144,10 @@ class ImageTransportHelper
   gpu::gles2::GLES2Decoder* Decoder();
 
   // IPC::Message handlers.
+#if defined(OS_MACOSX)
   void OnBufferPresented(
       const AcceleratedSurfaceMsg_BufferPresented_Params& params);
+#endif
   void OnWakeUpGpu();
 
   // Backbuffer resize callback.
@@ -180,8 +184,10 @@ class PassThroughImageTransportSurface
   virtual bool OnMakeCurrent(gfx::GLContext* context) override;
 
   // ImageTransportSurface implementation.
+#if defined(OS_MACOSX)
   virtual void OnBufferPresented(
       const AcceleratedSurfaceMsg_BufferPresented_Params& params) override;
+#endif
   virtual void OnResize(gfx::Size size, float scale_factor) override;
   virtual gfx::Size GetSize() override;
   virtual void SetLatencyInfo(