Let receiving() and SignalReceivingState be part of rtc::PacketTransportInterface.

webrtc/p2p/base/transportcontroller.cc

Index: webrtc/p2p/base/transportcontroller.cc
diff --git a/webrtc/p2p/base/transportcontroller.cc b/webrtc/p2p/base/transportcontroller.cc
index 9d5fb88b711c570f720bf7f466219fba0420510d..8dd748647b2a9175002912062e76ec5ed1cebefe 100644
--- a/webrtc/p2p/base/transportcontroller.cc
+++ b/webrtc/p2p/base/transportcontroller.cc
@@ -573,7 +573,8 @@ void TransportController::OnChannelWritableState_n(
   UpdateAggregateStates_n();
 }
 
-void TransportController::OnChannelReceivingState_n(TransportChannel* channel) {
+void TransportController::OnChannelReceivingState_n(
+    rtc::PacketTransportInterface* transport) {
   RTC_DCHECK(network_thread_->IsCurrent());
   UpdateAggregateStates_n();
 }