Remove the dependency of TransportChannel and TransportChannelImpl.

webrtc/p2p/base/packettransportinterface.h

 /*
  *  Copyright 2016 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.
  */
 
 #ifndef WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_
 #define WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_
 
 #include <string>
 #include <vector>
 
+#include "webrtc/base/asyncpacketsocket.h"

[Taylor Brandstetter, 2017/01/10 19:43:47]

Can you leave a comment that this included for PacketOptions?

[Zhi Huang, 2017/01/12 20:04:12]

Done.

 #include "webrtc/base/sigslot.h"
 #include "webrtc/base/socket.h"
 
 namespace cricket {
 class TransportChannel;
 }
 
 namespace rtc {
 struct PacketOptions;
 struct PacketTime;
@@ skipping 59 matching lines @@
       SignalReadPacket;
 
   // Signalled each time a packet is sent on this channel.
   sigslot::signal2<PacketTransportInterface*, const rtc::SentPacket&>
       SignalSentPacket;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_