Add support for dynamic channels in WebrtcTransport.

remoting/protocol/ice_connection_to_client.cc

Index: remoting/protocol/ice_connection_to_client.cc
diff --git a/remoting/protocol/ice_connection_to_client.cc b/remoting/protocol/ice_connection_to_client.cc
index 268eb9655736f2b480fbb6d9cdc6134e29463335..4a7dcf3720a328fd38133f508b525f8c231c48c7 100644
--- a/remoting/protocol/ice_connection_to_client.cc
+++ b/remoting/protocol/ice_connection_to_client.cc
@@ -170,6 +170,12 @@ void IceConnectionToClient::OnChannelInitialized(
   NotifyIfChannelsReady();
 }
 
+void IceConnectionToClient::OnChannelClosed(
+    ChannelDispatcherBase* channel_dispatcher) {
+  // ICE transport doesn't close channels dynamically.
+  NOTREACHED();
+}
+
 void IceConnectionToClient::NotifyIfChannelsReady() {
   DCHECK(thread_checker_.CalledOnValidThread());