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

webrtc/p2p/base/dtlstransportchannel.h

 /*
  *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 198 matching lines @@
  private:
   void OnWritableState(rtc::PacketTransportInterface* transport);
   void OnReadPacket(rtc::PacketTransportInterface* transport,
                     const char* data,
                     size_t size,
                     const rtc::PacketTime& packet_time,
                     int flags);
   void OnSentPacket(rtc::PacketTransportInterface* transport,
                     const rtc::SentPacket& sent_packet);
   void OnReadyToSend(rtc::PacketTransportInterface* transport);
-  void OnReceivingState(TransportChannel* channel);
+  void OnReceivingState(rtc::PacketTransportInterface* transport);
   void OnDtlsEvent(rtc::StreamInterface* stream_, int sig, int err);
   bool SetupDtls();
   void MaybeStartDtls();
   bool HandleDtlsPacket(const char* data, size_t size);
   void OnGatheringState(TransportChannelImpl* channel);
   void OnCandidateGathered(TransportChannelImpl* channel, const Candidate& c);
   void OnCandidatesRemoved(TransportChannelImpl* channel,
                            const Candidates& candidates);
   void OnRoleConflict(TransportChannelImpl* channel);
   void OnRouteChange(TransportChannel* channel, const Candidate& candidate);
@@ skipping 23 matching lines @@
   // transport channel became writable, or before a remote fingerprint was
   // received.
   rtc::Buffer cached_client_hello_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(DtlsTransportChannelWrapper);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_DTLSTRANSPORTCHANNEL_H_