Update from https://crrev.com/311076

net/quic/quic_sent_packet_manager.cc

 // 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.
 
 #include "net/quic/quic_sent_packet_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 830 matching lines @@
       // set the timer based on the earliest retransmittable packet.
       // Base the updated timer on the send time of the last packet.
       const QuicTime sent_time = unacked_packets_.GetLastPacketSentTime();
       const QuicTime tlp_time = sent_time.Add(GetTailLossProbeDelay());
       // Ensure the TLP timer never gets set to a time in the past.
       return QuicTime::Max(clock_->ApproximateNow(), tlp_time);
     }
     case RTO_MODE: {
       // The RTO is based on the first outstanding packet.
       const QuicTime sent_time =
-          unacked_packets_.GetFirstInFlightPacketSentTime();
+          FLAGS_quic_rto_uses_last_sent
+              ? unacked_packets_.GetLastPacketSentTime()
+              : unacked_packets_.GetFirstInFlightPacketSentTime();
       QuicTime rto_time = sent_time.Add(GetRetransmissionDelay());
       // Wait for TLP packets to be acked before an RTO fires.
       QuicTime tlp_time =
           unacked_packets_.GetLastPacketSentTime().Add(GetTailLossProbeDelay());
       return QuicTime::Max(tlp_time, rto_time);
     }
   }
   DCHECK(false);
   return QuicTime::Zero();
 }
@@ skipping 89 matching lines @@
   // Set up a pacing sender with a 1 millisecond alarm granularity, the same as
   // the default granularity of the Linux kernel's FQ qdisc.
   using_pacing_ = true;
   send_algorithm_.reset(
       new PacingSender(send_algorithm_.release(),
                        QuicTime::Delta::FromMilliseconds(1),
                        kInitialUnpacedBurst));
 }
 
 }  // namespace net