Remove the dependency of TransportChannel and TransportChannelImpl.

webrtc/p2p/base/icetransportinternal.h

Index: webrtc/p2p/base/icetransportinternal.h
diff --git a/webrtc/p2p/base/icetransportinternal.h b/webrtc/p2p/base/icetransportinternal.h
index 05939629f85d41db04300d66afee0609a07188be..0ac7974f1de92db2f2bdd74ffeb0d9c9f6820cb1 100644
--- a/webrtc/p2p/base/icetransportinternal.h
+++ b/webrtc/p2p/base/icetransportinternal.h
@@ -25,7 +25,11 @@ class MetricsObserverInterface;
 
 namespace cricket {
 
-// TODO(zhihuang): replace it with PeerConnectionInterface::IceConnectionState.
+class IceTransportInternal;
+typedef IceTransportInternal IceTransportInternal2;
+
+// TODO(zhihuang): Replace this with
+// PeerConnectionInterface::IceConnectionState.
 enum class IceTransportState {
   STATE_INIT,
   STATE_CONNECTING,  // Will enter this state once a connection is created
@@ -134,7 +138,7 @@ class IceTransportInternal : public rtc::PacketTransportInterface {
   sigslot::signal1<IceTransportInternal*> SignalDestroyed;
 
   // Debugging description of this transport.
-  const std::string debug_name() const override {
+  std::string debug_name() const override {
     return transport_name() + " " + std::to_string(component());
   }
 };