zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

content/common/gpu/gpu_channel_manager.h

Index: content/common/gpu/gpu_channel_manager.h
diff --git a/content/common/gpu/gpu_channel_manager.h b/content/common/gpu/gpu_channel_manager.h
index fc64d6c5d056dadc614dbf53fa82006d8014abdc..d62fe23eb406bb5752d76c8995bd2322a98b7696 100644
--- a/content/common/gpu/gpu_channel_manager.h
+++ b/content/common/gpu/gpu_channel_manager.h
@@ -24,6 +24,8 @@
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gl/gl_surface.h"
 
+struct GpuMsg_CreateGpuMemoryBuffer_Params;
+
 namespace base {
 class WaitableEvent;
 }
@@ -46,7 +48,6 @@ class ShaderTranslatorCache;
 namespace IPC {
 struct ChannelHandle;
 class SyncChannel;
-class MessageFilter;
 }
 
 struct GPUCreateCommandBufferConfig;
@@ -122,8 +123,9 @@ class CONTENT_EXPORT GpuChannelManager : public IPC::Listener,
       const GPUCreateCommandBufferConfig& init_params,
       int32 route_id);
   void OnLoadedShader(std::string shader);
+  void OnCreateGpuMemoryBuffer(
+      const GpuMsg_CreateGpuMemoryBuffer_Params& params);
   void DestroyGpuMemoryBuffer(gfx::GpuMemoryBufferId id, int client_id);
-  void DestroyGpuMemoryBufferOnIO(gfx::GpuMemoryBufferId id, int client_id);
   void OnDestroyGpuMemoryBuffer(gfx::GpuMemoryBufferId id,
                                 int client_id,
                                 int32 sync_point);
@@ -158,7 +160,6 @@ class CONTENT_EXPORT GpuChannelManager : public IPC::Listener,
   scoped_refptr<gfx::GLSurface> default_offscreen_surface_;
   scoped_ptr<GpuMemoryBufferFactory> gpu_memory_buffer_factory_;
   IPC::SyncChannel* channel_;
-  scoped_refptr<IPC::MessageFilter> filter_;
   bool relinquish_resources_pending_;
 
   // Member variables should appear before the WeakPtrFactory, to ensure