Use shared memory to update the renderer's view of the command buffer state.

content/common/gpu/gpu_command_buffer_stub.h

Index: content/common/gpu/gpu_command_buffer_stub.h
diff --git a/content/common/gpu/gpu_command_buffer_stub.h b/content/common/gpu/gpu_command_buffer_stub.h
index 61cd4796d6e36dc7950aaeca468075e4121002d9..144542ac1ac93dd18dd1800f8b1d6ad7616723a3 100644
--- a/content/common/gpu/gpu_command_buffer_stub.h
+++ b/content/common/gpu/gpu_command_buffer_stub.h
@@ -133,6 +133,7 @@ class GpuCommandBufferStub
   // Message handlers:
   void OnInitialize(IPC::Message* reply_message);
   void OnSetGetBuffer(int32 shm_id, IPC::Message* reply_message);
+  void OnSetSharedStateBuffer(int32 shm_id, IPC::Message* reply_message);
   void OnSetParent(int32 parent_route_id,
                    uint32 parent_texture_id,
                    IPC::Message* reply_message);