Allow cmdbuffer creation from compositor thread.

content/renderer/gpu/gpu_surface_proxy.h

Index: content/renderer/gpu/gpu_surface_proxy.h
diff --git a/content/renderer/gpu/gpu_surface_proxy.h b/content/renderer/gpu/gpu_surface_proxy.h
index 62cb41e51d4cf6c5c58909c72dba33c19c20cccf..f4f8879090e5dbb5759c8d715694fe451ecb643a 100644
--- a/content/renderer/gpu/gpu_surface_proxy.h
+++ b/content/renderer/gpu/gpu_surface_proxy.h
@@ -8,6 +8,7 @@
 
 #if defined(ENABLE_GPU)
 
+#include "base/memory/weak_ptr.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_message.h"
 
@@ -16,7 +17,8 @@ class Size;
 }
 
 // Client side proxy that forwards messages to a GpuSurfaceStub.
-class GpuSurfaceProxy : public IPC::Channel::Listener {
+class GpuSurfaceProxy : public IPC::Channel::Listener,
+                        public base::SupportsWeakPtr<GpuSurfaceProxy> {
  public:
   GpuSurfaceProxy(IPC::Channel::Sender* channel, int route_id);
   virtual ~GpuSurfaceProxy();