Update from https://crrev.com/305340

net/quic/congestion_control/tcp_cubic_sender.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/tcp_cubic_sender.h"
 
 #include <algorithm>
 
 #include "base/metrics/histogram.h"
 #include "net/quic/congestion_control/prr_sender.h"
 #include "net/quic/congestion_control/rtt_stats.h"
 #include "net/quic/crypto/crypto_protocol.h"
 
 using std::max;
 using std::min;
 
 namespace net {
 
 namespace {
 // Constants based on TCP defaults.
 // The minimum cwnd based on RFC 3782 (TCP NewReno) for cwnd reductions on a
 // fast retransmission.  The cwnd after a timeout is still 1.
 const QuicPacketCount kMinimumCongestionWindow = 2;
 const QuicByteCount kMaxSegmentSize = kDefaultTCPMSS;
 const int kMaxBurstLength = 3;
 const float kRenoBeta = 0.7f;  // Reno backoff factor.
 const uint32 kDefaultNumConnections = 2;  // N-connection emulation.
 }  // namespace
 
-TcpCubicSender::TcpCubicSender(
-    const QuicClock* clock,
-    const RttStats* rtt_stats,
-    bool reno,
-    QuicPacketCount initial_tcp_congestion_window,
-    QuicPacketCount max_tcp_congestion_window,
-    QuicConnectionStats* stats)
+TcpCubicSender::TcpCubicSender(const QuicClock* clock,
+                               const RttStats* rtt_stats,
+                               bool reno,
+                               QuicPacketCount initial_tcp_congestion_window,
+                               QuicPacketCount max_tcp_congestion_window,
+                               QuicConnectionStats* stats)
     : hybrid_slow_start_(clock),
       cubic_(clock, stats),
       rtt_stats_(rtt_stats),
       stats_(stats),
       reno_(reno),
       num_connections_(kDefaultNumConnections),
       congestion_window_count_(0),
       largest_sent_sequence_number_(0),
       largest_acked_sequence_number_(0),
       largest_sent_at_last_cutback_(0),
       congestion_window_(initial_tcp_congestion_window),
       previous_congestion_window_(0),
       slowstart_threshold_(max_tcp_congestion_window),
       previous_slowstart_threshold_(0),
       last_cutback_exited_slowstart_(false),
-      max_tcp_congestion_window_(max_tcp_congestion_window) {
-}
+      max_tcp_congestion_window_(max_tcp_congestion_window),
+      clock_(clock) {}
 
 TcpCubicSender::~TcpCubicSender() {
   UMA_HISTOGRAM_COUNTS("Net.QuicSession.FinalTcpCwnd", congestion_window_);
 }
 
 void TcpCubicSender::SetFromConfig(const QuicConfig& config,
                                    bool is_server,
                                    bool using_pacing) {
   if (is_server) {
     if (config.HasReceivedConnectionOptions() &&
         ContainsQuicTag(config.ReceivedConnectionOptions(), kIW10)) {
       // Initial window experiment.
       congestion_window_ = 10;
     }
     if (using_pacing) {
       // Disable the ack train mode in hystart when pacing is enabled, since it
       // may be falsely triggered.
       hybrid_slow_start_.set_ack_train_detection(false);
     }
   }
 }
 
+void TcpCubicSender::ResumeConnectionState(
+    const CachedNetworkParameters& cached_network_params) {
+  // If the previous bandwidth estimate is less than an hour old, store in
+  // preparation for doing bandwidth resumption.
+  int64 seconds_since_estimate =
+      clock_->WallNow().ToUNIXSeconds() - cached_network_params.timestamp();
+  if (seconds_since_estimate > kNumSecondsPerHour) {
+    return;
+  }
+
+  QuicBandwidth bandwidth = QuicBandwidth::FromBytesPerSecond(
+      cached_network_params.bandwidth_estimate_bytes_per_second());
+  QuicTime::Delta rtt_ms =
+      QuicTime::Delta::FromMilliseconds(cached_network_params.min_rtt_ms());
+  congestion_window_ = bandwidth.ToBytesPerPeriod(rtt_ms) / kMaxPacketSize;
+
+  // TODO(rjshade): Set appropriate CWND when previous connection was in slow
+  // start at time of estimate.
+}
+
 void TcpCubicSender::SetNumEmulatedConnections(int num_connections) {
   num_connections_ = max(1, num_connections);
   cubic_.SetNumConnections(num_connections_);
 }
 
 float TcpCubicSender::RenoBeta() const {
   // kNConnectionBeta is the backoff factor after loss for our N-connection
   // emulation, which emulates the effective backoff of an ensemble of N
   // TCP-Reno connections on a single loss event. The effective multiplier is
   // computed as:
@@ skipping 248 matching lines @@
   congestion_window_ = previous_congestion_window_;
   slowstart_threshold_ = previous_slowstart_threshold_;
   previous_congestion_window_ = 0;
 }
 
 CongestionControlType TcpCubicSender::GetCongestionControlType() const {
   return reno_ ? kReno : kCubic;
 }
 
 }  // namespace net