Add support for external video renderers in mojo.

media/mojo/services/mojo_renderer_impl.cc

Index: media/mojo/services/mojo_renderer_impl.cc
diff --git a/media/mojo/services/mojo_renderer_impl.cc b/media/mojo/services/mojo_renderer_impl.cc
index d5101f1546332c2857da10b312792433215ce0c5..84a44b6529bae76cf5cf2b28e7b323dcf3387769 100644
--- a/media/mojo/services/mojo_renderer_impl.cc
+++ b/media/mojo/services/mojo_renderer_impl.cc
@@ -115,13 +115,13 @@ bool MojoRendererImpl::HasAudio() {
   DVLOG(1) << __FUNCTION__;
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(remote_audio_renderer_.get());  // We always bind the renderer.
-  return true;
+  return demuxer_stream_provider_->GetStream(DemuxerStream::AUDIO);
 }
 
 bool MojoRendererImpl::HasVideo() {
   DVLOG(1) << __FUNCTION__;
   DCHECK(task_runner_->BelongsToCurrentThread());
-  return false;
+  return demuxer_stream_provider_->GetStream(DemuxerStream::VIDEO);
 }
 
 void MojoRendererImpl::SetCdm(MediaKeys* cdm) {