Allow cmdbuffer creation from compositor thread.

content/renderer/gpu/command_buffer_proxy.h

Index: content/renderer/gpu/command_buffer_proxy.h
diff --git a/content/renderer/gpu/command_buffer_proxy.h b/content/renderer/gpu/command_buffer_proxy.h
index 26687b9ee35f9fd0af86126a077307c20591f2c8..a5dd516bd6111537cb7a71eb37aa4e6832cfa1fa 100644
--- a/content/renderer/gpu/command_buffer_proxy.h
+++ b/content/renderer/gpu/command_buffer_proxy.h
@@ -14,6 +14,7 @@
 #include "base/callback_old.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "content/renderer/gpu/gpu_channel_host.h"
 #include "content/renderer/gpu/gpu_video_decode_accelerator_host.h"
 #include "gpu/command_buffer/common/command_buffer.h"
 #include "ipc/ipc_channel.h"
@@ -33,7 +34,8 @@ class Task;
 // Client side proxy that forwards messages synchronously to a
 // CommandBufferStub.
 class CommandBufferProxy : public gpu::CommandBuffer,
-                           public IPC::Channel::Listener {
+                           public IPC::Channel::Listener,
+                           public GpuChannelHost::MessageFilter::Listener {
  public:
   CommandBufferProxy(IPC::Channel::Sender* channel, int route_id);
   virtual ~CommandBufferProxy();