Proxy RtcVideoDecoder calls to a media::VideoDecoder.

content/renderer/media/webrtc/peer_connection_dependency_factory.h

Index: content/renderer/media/webrtc/peer_connection_dependency_factory.h
diff --git a/content/renderer/media/webrtc/peer_connection_dependency_factory.h b/content/renderer/media/webrtc/peer_connection_dependency_factory.h
index 4f52425d31884f1a2e36bd01a95e0e98cd4faafc..f4ca1ed08698df052a7b517c08dee91bcc629807 100644
--- a/content/renderer/media/webrtc/peer_connection_dependency_factory.h
+++ b/content/renderer/media/webrtc/peer_connection_dependency_factory.h
@@ -25,6 +25,7 @@ class WaitableEvent;
 
 namespace media {
 class GpuVideoAcceleratorFactories;
+class VideoDecoder;
 }
 
 namespace rtc {
@@ -132,8 +133,14 @@ class CONTENT_EXPORT PeerConnectionDependencyFactory
   // creating PeerConnection objects.
   void CreatePeerConnectionFactory();
 
+  // A factory closure which can be run to create a media::VideoDecoder.
+  using CreateVideoDecoderCB =
+      base::Callback<std::unique_ptr<media::VideoDecoder>()>;
+
   void InitializeSignalingThread(
       media::GpuVideoAcceleratorFactories* gpu_factories,
+      const CreateVideoDecoderCB& create_video_decoder_cb,
+      const scoped_refptr<base::SingleThreadTaskRunner>& decoder_task_runner,
       base::WaitableEvent* event);
 
   void InitializeWorkerThread(rtc::Thread** thread,