Update from https://crrev.com/309415

net/quic/congestion_control/hybrid_slow_start.cc

 // Copyright (c) 2012 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/congestion_control/hybrid_slow_start.h"
 
 #include <algorithm>
 
 using std::max;
 using std::min;
 
 namespace net {
 
 // Note(pwestin): the magic clamping numbers come from the original code in
 // tcp_cubic.c.
 const int64 kHybridStartLowWindow = 16;
 // Number of delay samples for detecting the increase of delay.
 const uint32 kHybridStartMinSamples = 8;
-const int kHybridStartDelayFactorExp = 4;  // 2^4 = 16
+// Exit slow start if the min rtt has increased by more than 1/8th.
+const int kHybridStartDelayFactorExp = 3;  // 2^3 = 8
 // The original paper specifies 2 and 8ms, but those have changed over time.
 const int64 kHybridStartDelayMinThresholdUs = 4000;
 const int64 kHybridStartDelayMaxThresholdUs = 16000;
 
 HybridSlowStart::HybridSlowStart(const QuicClock* clock)
     : clock_(clock),
       ack_train_detection_(true),
       started_(false),
       hystart_found_(NOT_FOUND),
       last_sent_sequence_number_(0),
@@ skipping 96 matching lines @@
       hystart_found_= DELAY;
     }
   }
   // Exit from slow start if the cwnd is greater than 16 and an ack train or
   // increasing delay are found.
   return congestion_window >= kHybridStartLowWindow &&
       hystart_found_ != NOT_FOUND;
 }
 
 }  // namespace net