Add following helper methods to track successful QUIC client port migrations:

net/quic/quic_sent_packet_manager.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_
 #define NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_
 
 #include <deque>
 #include <list>
 #include <map>
@@ skipping 162 matching lines @@
   // Enables pacing if it has not already been enabled, and if
   // FLAGS_enable_quic_pacing is set.
   void MaybeEnablePacing();
 
   bool using_pacing() const { return using_pacing_; }
 
   void set_debug_delegate(DebugDelegate* debug_delegate) {
     debug_delegate_ = debug_delegate;
   }
 
+  QuicPacketSequenceNumber largest_observed() const {
+    return largest_observed_;
+  }
+
  private:
   friend class test::QuicConnectionPeer;
   friend class test::QuicSentPacketManagerPeer;
 
   // The retransmission timer is a single timer which switches modes depending
   // upon connection state.
   enum RetransmissionTimeoutMode {
     // A conventional TCP style RTO.
     RTO_MODE,
     // A tail loss probe.  By default, QUIC sends up to two before RTOing.
@@ skipping 119 matching lines @@
   // Sets of packets acked and lost as a result of the last congestion event.
   SendAlgorithmInterface::CongestionMap packets_acked_;
   SendAlgorithmInterface::CongestionMap packets_lost_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicSentPacketManager);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_