Update from https://crrev.com/311076

net/quic/congestion_control/tcp_cubic_sender_test.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 <algorithm>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/quic/congestion_control/rtt_stats.h"
 #include "net/quic/congestion_control/tcp_cubic_sender.h"
@@ skipping 432 matching lines @@
 
 TEST_F(TcpCubicSenderTest, RTOCongestionWindowNoRetransmission) {
   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 
   // Expect the window to remain unchanged if the RTO fires but no
   // packets are retransmitted.
   sender_->OnRetransmissionTimeout(false);
   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 }
 
+TEST_F(TcpCubicSenderTest, RTOTwiceOnlyHalvesSsthresh) {
+  EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
+
+  sender_->OnRetransmissionTimeout(true);
+  EXPECT_EQ(2 * kDefaultTCPMSS, sender_->GetCongestionWindow());
+  EXPECT_EQ(5u, sender_->slowstart_threshold());
+
+  sender_->OnRetransmissionTimeout(true);
+  EXPECT_EQ(2 * kDefaultTCPMSS, sender_->GetCongestionWindow());
+  EXPECT_EQ(5u, sender_->slowstart_threshold());
+
+  AckNPackets(2);
+
+  EXPECT_EQ(4 * kDefaultTCPMSS, sender_->GetCongestionWindow());
+  EXPECT_EQ(5u, sender_->slowstart_threshold());
+
+  sender_->OnRetransmissionTimeout(true);
+  EXPECT_EQ(2 * kDefaultTCPMSS, sender_->GetCongestionWindow());
+  EXPECT_EQ(2u, sender_->slowstart_threshold());
+}
+
 TEST_F(TcpCubicSenderTest, RetransmissionDelay) {
   const int64 kRttMs = 10;
   const int64 kDeviationMs = 3;
   EXPECT_EQ(QuicTime::Delta::Zero(), sender_->RetransmissionDelay());
 
   sender_->rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(kRttMs),
                                 QuicTime::Delta::Zero(), clock_.Now());
 
   // Initial value is to set the median deviation to half of the initial
   // rtt, the median in then multiplied by a factor of 4 and finally the
@@ skipping 272 matching lines @@
 
   cached_network_params.set_bandwidth_estimate_bytes_per_second(
       (kMinCongestionWindowForBandwidthResumption - 1) * kMaxPacketSize);
   EXPECT_TRUE(sender_->ResumeConnectionState(cached_network_params));
   EXPECT_EQ(kMinCongestionWindowForBandwidthResumption,
             sender_->congestion_window());
 }
 
 }  // namespace test
 }  // namespace net