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..9012168d435e0ef19269b9230a02cddd3b6acb4a 100644
--- a/content/renderer/gpu/gpu_video_decode_accelerator_host.h
+++ b/content/renderer/gpu/gpu_video_decode_accelerator_host.h
@@ -9,23 +9,31 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
+#include "base/threading/non_thread_safe.h"
 #include "ipc/ipc_channel.h"
 #include "media/video/video_decode_accelerator.h"
 
 class MessageLoop;
 class MessageRouter;
+namespace gpu {
+class CommandBufferHelper;
+class ReadWriteTokens;
+}
 
 // This class is used to talk to VideoDecodeAccelerator in the Gpu process
 // through IPC messages.
-class GpuVideoDecodeAcceleratorHost : public IPC::Channel::Listener,
-                                      public media::VideoDecodeAccelerator {
+class GpuVideoDecodeAcceleratorHost
+    : public IPC::Channel::Listener,
+      public media::VideoDecodeAccelerator,
+      public base::NonThreadSafe {
  public:
   // |router| is used to dispatch IPC messages to this object.
   // |ipc_sender| is used to send IPC messages to Gpu process.
   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 +47,20 @@ 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 token-pair suitable for
+  // sending over IPC for synchronization with the command buffer.
+  gpu::ReadWriteTokens SyncTokens();
+
   void OnBitstreamBufferProcessed(int32 bitstream_buffer_id);
   void OnProvidePictureBuffer(
     uint32 num_requested_buffers, const gfx::Size& buffer_size, int32 mem_type);
@@ -78,7 +90,18 @@ 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_;
+  // TODO(fischman): storing route_id's for GPU process entities in the renderer
+  // process is vulnerable to GPU process crashing & being respawned, and
+  // attempting to use an outdated or reused route id.
+  int32 command_buffer_route_id_;
+
+  // Helper for the command buffer associated with the context the GPU Video
+  // Decoder uses.
+  // TODO(fischman): in the out-of-process case, this won't work
+  // (context3d->gles2_impl() will be NULL), and will have to be replaced with a
+  // dedicated message such as WaitForToken, which will serialize subsequent
+  // message processing behind it.
+  gpu::CommandBufferHelper* cmd_buffer_helper_;
 
   // Temporarily store configs here in between Create and Initialize phase.
   std::vector<uint32> configs_;