Add a merely pass-through QuicMultipathSentPacketManager. Protected behind blocked flag FLAGS_quic_…

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 <stddef.h>
 
 #include <map>
@@ skipping 149 matching lines @@
   // Returns the current delay for the retransmission timer, which may send
   // either a tail loss probe or do a full RTO.  Returns QuicTime::Zero() if
   // there are no retransmittable packets.
   const QuicTime GetRetransmissionTime() const override;
 
   const RttStats* GetRttStats() const override;
 
   // Returns the estimated bandwidth calculated by the congestion algorithm.
   QuicBandwidth BandwidthEstimate() const override;
 
-  const QuicSustainedBandwidthRecorder& SustainedBandwidthRecorder()
+  const QuicSustainedBandwidthRecorder* SustainedBandwidthRecorder()
       const override;
 
   // Returns the size of the current congestion window in number of
   // kDefaultTCPMSS-sized segments. Note, this is not the *available* window.
   // Some send algorithms may not use a congestion window and will return 0.
   QuicPacketCount GetCongestionWindowInTcpMss() const override;
 
   // Returns the number of packets of length |max_packet_length| which fit in
   // the current congestion window. More packets may end up in flight if the
   // congestion window has been recently reduced, of if non-full packets are
@@ skipping 222 matching lines @@
   // Records bandwidth from server to client in normal operation, over periods
   // of time with no loss events.
   QuicSustainedBandwidthRecorder sustained_bandwidth_recorder_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicSentPacketManager);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_