Introduce rtc::PacketTransportInterface and let cricket::TransportChannel inherit.

webrtc/p2p/p2p.gyp

 # Copyright (c) 2014 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.
 
 {
   'includes': [ '../build/common.gypi', ],
@@ skipping 14 matching lines @@
         'base/common.h',
         'base/dtlstransport.h',
         'base/dtlstransportchannel.cc',
         'base/dtlstransportchannel.h',
         'base/p2pconstants.cc',
         'base/p2pconstants.h',
         'base/p2ptransport.cc',
         'base/p2ptransport.h',
         'base/p2ptransportchannel.cc',
         'base/p2ptransportchannel.h',
+        'base/packettransportinterface.h',
         'base/packetsocketfactory.h',
         'base/port.cc',
         'base/port.h',
         'base/portallocator.cc',
         'base/portallocator.h',
         'base/portinterface.h',
         'base/pseudotcp.cc',
         'base/pseudotcp.h',
         'base/relayport.cc',
         'base/relayport.h',
@@ skipping 89 matching lines @@
         'libstunprober',
         'rtc_p2p'
       ],
       'sources': [
         'stunprober/main.cc',
       ],
     },
   ],  # targets
 }