Implement proper synchronization between HW video decode IPC and CommandBuffer.

content/renderer/gpu/gpu_video_decode_accelerator_host.h

Index: content/renderer/gpu/gpu_video_decode_accelerator_host.h
diff --git a/content/renderer/gpu/gpu_video_decode_accelerator_host.h b/content/renderer/gpu/gpu_video_decode_accelerator_host.h
index ea73da0ba3ff131492094521c60e90869c0c6965..4cc0746baa1cf701a57deb79ca33f26fcd2ac7ce 100644
--- a/content/renderer/gpu/gpu_video_decode_accelerator_host.h
+++ b/content/renderer/gpu/gpu_video_decode_accelerator_host.h
@@ -14,6 +14,9 @@
 
 class MessageLoop;
 class MessageRouter;
+namespace gpu {
+class CommandBufferHelper;
+}
 
 // This class is used to talk to VideoDecodeAccelerator in the Gpu process
 // through IPC messages.
@@ -25,7 +28,8 @@ class GpuVideoDecodeAcceleratorHost : public IPC::Channel::Listener,
   GpuVideoDecodeAcceleratorHost(MessageRouter* router,
                                 IPC::Message::Sender* ipc_sender,
                                 int32 decoder_host_id,
-                                uint32 command_buffer_route_id,
+                                int32 command_buffer_route_id,
+                                gpu::CommandBufferHelper* cmd_buffer_helper,
                                 media::VideoDecodeAccelerator::Client* client);
   virtual ~GpuVideoDecodeAcceleratorHost();
 
@@ -39,16 +43,20 @@ class GpuVideoDecodeAcceleratorHost : public IPC::Channel::Listener,
       const std::vector<uint32>& requested_configs,
       std::vector<uint32>* matched_configs) OVERRIDE;
   virtual bool Initialize(const std::vector<uint32>& configs) OVERRIDE;
-  virtual bool Decode(const media::BitstreamBuffer& bitstream_buffer) OVERRIDE;
+  virtual void Decode(const media::BitstreamBuffer& bitstream_buffer) OVERRIDE;
   virtual void AssignGLESBuffers(
       const std::vector<media::GLESBuffer>& buffers) OVERRIDE;
   virtual void AssignSysmemBuffers(
       const std::vector<media::SysmemBuffer>& buffers) OVERRIDE;
   virtual void ReusePictureBuffer(int32 picture_buffer_id) OVERRIDE;
-  virtual bool Flush() OVERRIDE;
-  virtual bool Abort() OVERRIDE;
+  virtual void Flush() OVERRIDE;
+  virtual void Abort() OVERRIDE;
 
  private:
+  // Insert a token into the command buffer and return a <read,write> token pair
+  // suitable for sending over IPC.
+  std::pair<int32, int32> SyncTokens();
+
   void OnBitstreamBufferProcessed(int32 bitstream_buffer_id);
   void OnProvidePictureBuffer(
     uint32 num_requested_buffers, const gfx::Size& buffer_size, int32 mem_type);
@@ -78,7 +86,11 @@ class GpuVideoDecodeAcceleratorHost : public IPC::Channel::Listener,
 
   // Route ID for the command buffer associated with the context the GPU Video
   // Decoder uses.
-  uint32 command_buffer_route_id_;
+  int32 command_buffer_route_id_;
+
+  // Helper for the command buffer associated with the context the GPU Video
+  // Decoder uses.
+  gpu::CommandBufferHelper* cmd_buffer_helper_;
 
   // Temporarily store configs here in between Create and Initialize phase.
   std::vector<uint32> configs_;
@@ -86,6 +98,10 @@ class GpuVideoDecodeAcceleratorHost : public IPC::Channel::Listener,
   // Reference to the client that will receive callbacks from the decoder.
   media::VideoDecodeAccelerator::Client* client_;
 
+  // MessageLoop on which this object was created.  All Send()'s are trampolined
+  // to this loop if they are not issued on it by the client.
+  MessageLoop* message_loop_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuVideoDecodeAcceleratorHost);
 };