Make RendererGpuVideoDecoderFactories live on arbitrary threads.

content/renderer/media/rtc_video_decoder.h

Index: content/renderer/media/rtc_video_decoder.h
diff --git a/content/renderer/media/rtc_video_decoder.h b/content/renderer/media/rtc_video_decoder.h
index 8c4c195fe1302b86914e52fc7956959ee03bb63a..56f19260613d7ceef945da7245a805df7e69d58a 100644
--- a/content/renderer/media/rtc_video_decoder.h
+++ b/content/renderer/media/rtc_video_decoder.h
@@ -35,13 +35,11 @@ class DecoderBuffer;
 namespace content {
 
 // This class uses hardware accelerated video decoder to decode video for
-// WebRTC. The message loop of RendererGpuVideoDecoderFactories is stored as
-// |vda_message_loop_|. It is the compositor thread, or the renderer thread if
-// threaded compositing is disabled. VDA::Client methods run on
-// |vda_message_loop_|. webrtc::VideoDecoder methods run on WebRTC
+// WebRTC. |vda_message_loop_| is the message loop proxy of the media thread,
+// which VDA::Client methods run on. webrtc::VideoDecoder methods run on WebRTC
 // DecodingThread or Chrome_libJingle_WorkerThread, which are trampolined to
 // |vda_message_loop_|. Decode() is non-blocking and queues the buffers. Decoded
-// frames are delivered on |vda_message_loop_|.
+// frames are delivered to WebRTC on |vda_message_loop_|.
 class CONTENT_EXPORT RTCVideoDecoder
     : NON_EXPORTED_BASE(public webrtc::VideoDecoder),
       public media::VideoDecodeAccelerator::Client,
@@ -49,8 +47,11 @@ class CONTENT_EXPORT RTCVideoDecoder
  public:
   virtual ~RTCVideoDecoder();
 
-  // Creates a RTCVideoDecoder. Returns NULL if failed.
+  // Creates a RTCVideoDecoder. Returns NULL if failed. |vda_loop_proxy| should
+  // be the same as the one running |factories|.
   static scoped_ptr<RTCVideoDecoder> Create(
+      webrtc::VideoCodecType type,
+      const scoped_refptr<base::MessageLoopProxy> vda_loop_proxy,
       const scoped_refptr<media::GpuVideoDecoder::Factories>& factories);
 
   // webrtc::VideoDecoder implementation.
@@ -110,7 +111,9 @@ class CONTENT_EXPORT RTCVideoDecoder
 
   FRIEND_TEST_ALL_PREFIXES(RTCVideoDecoderTest, IsBufferAfterReset);
 
+  // |vda_loop_proxy| should be the same as the one running |factories|.
   RTCVideoDecoder(
+      const scoped_refptr<base::MessageLoopProxy>& vda_loop_proxy,
       const scoped_refptr<media::GpuVideoDecoder::Factories>& factories);
 
   void Initialize(base::WaitableEvent* waiter);
@@ -147,6 +150,7 @@ class CONTENT_EXPORT RTCVideoDecoder
 
   // Resets VDA.
   void ResetInternal();
+  void ReleaseInternal();

[Ami GONE FROM CHROMIUM, 2013/07/22 19:46:21]

Any reason for this, given it's no different from DestroyVDA()?

(if you keep it, you should doco its purpose)

[wuchengli, 2013/07/23 16:29:28]

You are right. ReleaseInternal is not required.

 
   // Tells VDA that a picture buffer can be recycled.
   void ReusePictureBuffer(int64 picture_buffer_id, uint32 sync_point);
@@ -201,15 +205,6 @@ class CONTENT_EXPORT RTCVideoDecoder
   // of |factories_|.
   scoped_refptr<base::MessageLoopProxy> vda_loop_proxy_;
 
-  // The thread to create shared memory. Factories::CreateSharedMemory is
-  // trampolined to the child thread. When |vda_loop_proxy_| is the compositor
-  // thread, blocking on the child thread will deadlock. During WebRTC hang up,
-  // the child thread waits for Chrome_libJingle_WorkerThread. libJingle thread
-  // cannot finish when DecodingThread holds a WebRTC lock and blocks on the
-  // child thread. So we need to call CreateSharedMemory asynchronously from a
-  // different thread.
-  base::Thread create_shm_thread_;
-
   // The texture target used for decoded pictures.
   uint32 decoder_texture_target_;