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>
 
+// This is included for PacketOptions.
+#include "webrtc/base/asyncpacketsocket.h"
 #include "webrtc/base/sigslot.h"
 #include "webrtc/base/socket.h"
 
 namespace cricket {
 class TransportChannel;
 }
 
 namespace rtc {
 struct PacketOptions;
 struct PacketTime;
 struct SentPacket;
 
 class PacketTransportInterface : public sigslot::has_slots<> {
  public:
   virtual ~PacketTransportInterface() {}
 
   // Identify the object for logging and debug purpose.
-  virtual const std::string debug_name() const = 0;
+  virtual std::string debug_name() const = 0;
 
   // The transport has been established.
   virtual bool writable() const = 0;
 
   // The transport has received a packet in the last X milliseconds, here X is
   // configured by each implementation.
   virtual bool receiving() const = 0;
 
   // Attempts to send the given packet.
   // The return value is < 0 on failure. The return value in failure case is not
@@ skipping 41 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_