Make RendererGpuVideoDecoderFactories live on arbitrary threads.

content/renderer/media/rtc_video_decoder_factory.cc

 // Copyright 2013 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.
 
 #include "content/renderer/media/rtc_video_decoder_factory.h"
 
 #include "base/location.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/renderer/media/rtc_video_decoder.h"
 
 namespace content {
 
 RTCVideoDecoderFactory::RTCVideoDecoderFactory(
-    const scoped_refptr<media::GpuVideoDecoder::Factories>& gpu_factories)
-    : vda_loop_proxy_(gpu_factories->GetMessageLoop()) {
+    scoped_ptr<base::Thread> vda_thread,
+    const scoped_refptr<content::RendererGpuVideoDecoderFactories>&
+        gpu_factories)
+    : vda_thread_(vda_thread.Pass()), gpu_factories_(gpu_factories) {
   DVLOG(2) << "RTCVideoDecoderFactory";
-  // The decoder cannot be created in CreateVideoDecoder because VDA has to be
-  // created on |vda_loop_proxy_|, which can be the child thread. The child
-  // thread is blocked when CreateVideoDecoder runs. This supports only one
-  // VDA-powered <video> tag at a time.
-  // TODO(wuchengli): remove this restriction.
-  // |decoder_| can be null if VDA does not support VP8.
-  decoder_ = RTCVideoDecoder::Create(gpu_factories);
 }
 
 RTCVideoDecoderFactory::~RTCVideoDecoderFactory() {
   DVLOG(2) << "~RTCVideoDecoderFactory";
-  if (decoder_) {
-    webrtc::VideoDecoder* decoder = decoder_.release();
-    if (!vda_loop_proxy_->DeleteSoon(FROM_HERE, decoder))
-      delete decoder;
-  }
 }
 
 webrtc::VideoDecoder* RTCVideoDecoderFactory::CreateVideoDecoder(
     webrtc::VideoCodecType type) {
   DVLOG(2) << "CreateVideoDecoder";
-  // Only VP8 is supported.
-  if (type == webrtc::kVideoCodecVP8)
-    return decoder_.release();
-  return NULL;
+  scoped_ptr<RTCVideoDecoder> decoder =
+      RTCVideoDecoder::Create(type, gpu_factories_->Clone());

[scherkus (not reviewing), 2013/07/18 00:54:43]

can we call
RenderThreadImpl::current()->GetGpuFactories(vda_thread_->message_loop_proxy())
instead of Clone(), or is the issue that CVD() isn't called on the main thread?

[wuchengli, 2013/07/18 09:42:00]

CVD() is called on Chrome_libJingle_WorkerThread and the main thread is blocked
while this runs.

+  return decoder.release();
 }
 
 void RTCVideoDecoderFactory::DestroyVideoDecoder(
     webrtc::VideoDecoder* decoder) {
   DVLOG(2) << "DestroyVideoDecoder";
-  // Save back the decoder because it is the only one. VideoDecoder::Release
-  // should have been called.
-  decoder->RegisterDecodeCompleteCallback(NULL);
-  decoder_.reset(decoder);
+  if (!vda_thread_->message_loop_proxy()->DeleteSoon(FROM_HERE, decoder))
+    delete decoder;
 }
 
 }  // namespace content