Cast: Implement priority packets in PacedSender

media/cast/net/cast_transport_sender_impl.cc

Index: media/cast/net/cast_transport_sender_impl.cc
diff --git a/media/cast/net/cast_transport_sender_impl.cc b/media/cast/net/cast_transport_sender_impl.cc
index 1e3f71845881ed1d4f59614ee4e83747050f68a5..973f34155fd1f347b9922192cd669fc2aa668059 100644
--- a/media/cast/net/cast_transport_sender_impl.cc
+++ b/media/cast/net/cast_transport_sender_impl.cc
@@ -89,7 +89,9 @@ void CastTransportSenderImpl::InitializeAudio(
   }
   audio_sender_.reset(new RtpSender(clock_, transport_task_runner_, &pacer_));
   if (audio_sender_->Initialize(config)) {
+    // Audio packets have a higher priority.
     pacer_.RegisterAudioSsrc(config.ssrc);
+    pacer_.RegisterPrioritySsrc(config.ssrc);
     status_callback_.Run(TRANSPORT_AUDIO_INITIALIZED);
   } else {
     audio_sender_.reset();