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

content/common/gpu/client/command_buffer_proxy.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_GPU_CLIENT_COMMAND_BUFFER_PROXY_H_
 #define CONTENT_COMMON_GPU_CLIENT_COMMAND_BUFFER_PROXY_H_
 #pragma once
 
 #if defined(ENABLE_GPU)
 
 #include <map>
 #include <queue>
 #include <string>
 
 #include "base/callback.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "content/common/gpu/client/gpu_video_decode_accelerator_host.h"
 #include "gpu/command_buffer/common/command_buffer.h"
+#include "gpu/command_buffer/common/command_buffer_shared.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_message.h"
 
 class GpuChannelHost;
 struct GPUCommandBufferConsoleMessage;
 
 namespace base {
 class SharedMemory;
 }
 
@@ skipping 78 matching lines @@
   // verify that the context has not been lost.
   bool Send(IPC::Message* msg);
 
   // Message handlers:
   void OnUpdateState(const gpu::CommandBuffer::State& state);
   void OnNotifyRepaint();
   void OnDestroyed(gpu::error::ContextLostReason reason);
   void OnEchoAck();
   void OnConsoleMessage(const GPUCommandBufferConsoleMessage& message);
 
+  // Try to read an updated copy of the state from shared memory.
+  void TryUpdateState();
+
   // Local cache of id to transfer buffer mapping.
   typedef std::map<int32, gpu::Buffer> TransferBufferMap;
   TransferBufferMap transfer_buffers_;
 
   // Zero or more video decoder hosts owned by this proxy, keyed by their
   // decoder_route_id.
   typedef std::map<int, scoped_refptr<GpuVideoDecodeAcceleratorHost> > Decoders;
   Decoders video_decoder_hosts_;
 
   // The last cached state received from the service.
   State last_state_;

[apatrick_chromium, 2012/02/13 20:50:58]

Do we need to have two copied of the shared state? It seems redundant.

 
+  // The shared memory area used to update state.
+  gpu::CommandBufferSharedState* shared_state_;
+
   // |*this| is owned by |*channel_| and so is always outlived by it, so using a
   // raw pointer is ok.
   GpuChannelHost* channel_;
   int route_id_;
   unsigned int flush_count_;
 
   // Tasks to be invoked in echo responses.
   std::queue<base::Closure> echo_tasks_;
 
   base::Closure notify_repaint_task_;
 
   base::Closure channel_error_callback_;
 
   GpuConsoleMessageCallback console_message_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(CommandBufferProxy);
 };
 
 #endif  // ENABLE_GPU
 
 #endif  // CONTENT_COMMON_GPU_CLIENT_COMMAND_BUFFER_PROXY_H_