Add audio support in WebrtcConnectionToHost, audio unittest

remoting/protocol/webrtc_transport.h

Index: remoting/protocol/webrtc_transport.h
diff --git a/remoting/protocol/webrtc_transport.h b/remoting/protocol/webrtc_transport.h
index 0746425326890e01929c1f2d345fa4c3a70b5976..8e5fb1bce4493a65bfb403b83324cccac11e2f67 100644
--- a/remoting/protocol/webrtc_transport.h
+++ b/remoting/protocol/webrtc_transport.h
@@ -71,6 +71,7 @@ class WebrtcTransport : public Transport {
   WebrtcDummyVideoEncoderFactory* video_encoder_factory() {
     return video_encoder_factory_;
   }
+  WebrtcAudioModule* audio_module();
 
   // Creates outgoing data channel. The channel is created in CONNECTING state.
   // The caller must wait for OnMessagePipeOpen() notification before sending
@@ -123,7 +124,6 @@ class WebrtcTransport : public Transport {
 
   base::ThreadChecker thread_checker_;
 
-  rtc::Thread* worker_thread_;
   scoped_refptr<TransportContext> transport_context_;
   EventHandler* event_handler_ = nullptr;
   SendTransportInfoCallback send_transport_info_callback_;