Add MessageChanneFactory interface and use it in ChannelDispatcherBase.

remoting/protocol/webrtc_connection_to_host.cc

Index: remoting/protocol/webrtc_connection_to_host.cc
diff --git a/remoting/protocol/webrtc_connection_to_host.cc b/remoting/protocol/webrtc_connection_to_host.cc
index 351bb8d3535b06540e519069fc2ae0a818280a47..bfa103ea5f2ff0241b84fe26db0f946d40f81ac6 100644
--- a/remoting/protocol/webrtc_connection_to_host.cc
+++ b/remoting/protocol/webrtc_connection_to_host.cc
@@ -139,14 +139,6 @@ void WebrtcConnectionToHost::OnChannelInitialized(
   NotifyIfChannelsReady();
 }
 
-void WebrtcConnectionToHost::OnChannelError(
-    ChannelDispatcherBase* channel_dispatcher,
-    ErrorCode error) {
-  LOG(ERROR) << "Failed to connect channel " << channel_dispatcher;
-  CloseChannels();
-  SetState(FAILED, CHANNEL_CONNECTION_ERROR);
-}
-
 ConnectionToHost::State WebrtcConnectionToHost::state() const {
   return state_;
 }