Add the last_sent_packet_id to the candidate pair change signal

webrtc/p2p/base/p2ptransportchannel.h

 /*
  *  Copyright 2004 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 175 matching lines @@
   // Public for unit tests.
   PortAllocatorSession* allocator_session() {
     return allocator_sessions_.back();
   }
 
   // Public for unit tests.
   const std::vector<RemoteCandidate>& remote_candidates() const {
     return remote_candidates_;
   }
 
+  // For unit tests only.
+  void set_last_sent_packet_id(int packet_id) {
+    last_sent_packet_id_ = packet_id;
+  }

[Taylor Brandstetter, 2016/03/30 21:17:14]

Why is this necessary? Can't SendPacket be used by the unit tests?

[honghaiz3, 2016/03/30 21:48:09]

Good point. I removed this and revised the tests with SendPacket. 

+
  private:
   rtc::Thread* thread() { return worker_thread_; }
   bool IsGettingPorts() { return allocator_session()->IsGettingPorts(); }
 
   // A transport channel is weak if the current best connection is either
   // not receiving or not writable, or if there is no best connection at all.
   bool weak() const;
   void UpdateConnectionStates();
   void RequestSort();
   void SortConnections();
@@ skipping 113 matching lines @@
   IceMode remote_ice_mode_;
   IceRole ice_role_;
   uint64_t tiebreaker_;
   IceGatheringState gathering_state_;
 
   int check_receiving_interval_;
   int64_t last_ping_sent_ms_ = 0;
   int weak_ping_interval_ = WEAK_PING_INTERVAL;
   TransportChannelState state_ = TransportChannelState::STATE_INIT;
   IceConfig config_;
+  int last_sent_packet_id_ = -1;  // -1 indicates no packet was sent before.
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_P2PTRANSPORTCHANNEL_H_