Repair the CWND reduction caused by spurious RTO's in QUIC's congestion

net/quic/congestion_control/tcp_cubic_sender.h

 // 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.
 //
 // TCP cubic send side congestion algorithm, emulates the behavior of
 // TCP cubic.
 
 #ifndef NET_QUIC_CONGESTION_CONTROL_TCP_CUBIC_SENDER_H_
 #define NET_QUIC_CONGESTION_CONTROL_TCP_CUBIC_SENDER_H_
 
@@ skipping 36 matching lines @@
   virtual void OnCongestionEvent(bool rtt_updated,
                                  QuicByteCount bytes_in_flight,
                                  const CongestionMap& acked_packets,
                                  const CongestionMap& lost_packets) OVERRIDE;
   virtual bool OnPacketSent(QuicTime sent_time,
                             QuicByteCount bytes_in_flight,
                             QuicPacketSequenceNumber sequence_number,
                             QuicByteCount bytes,
                             HasRetransmittableData is_retransmittable) OVERRIDE;
   virtual void OnRetransmissionTimeout(bool packets_retransmitted) OVERRIDE;
+  virtual void RevertRetransmissionTimeout() OVERRIDE;
   virtual QuicTime::Delta TimeUntilSend(
       QuicTime now,
       QuicByteCount bytes_in_flight,
       HasRetransmittableData has_retransmittable_data) const OVERRIDE;
   virtual QuicBandwidth BandwidthEstimate() const OVERRIDE;
   virtual QuicTime::Delta RetransmissionDelay() const OVERRIDE;
   virtual QuicByteCount GetCongestionWindow() const OVERRIDE;
   // End implementation of SendAlgorithmInterface.
 
  private:
@@ skipping 44 matching lines @@
 
   // Track the largest packet that has been acked.
   QuicPacketSequenceNumber largest_acked_sequence_number_;
 
   // Track the largest sequence number outstanding when a CWND cutback occurs.
   QuicPacketSequenceNumber largest_sent_at_last_cutback_;
 
   // Congestion window in packets.
   QuicTcpCongestionWindow congestion_window_;
 
+  // Congestion window before the last loss event or RTO.
+  QuicByteCount previous_congestion_window_;
+
   // Slow start congestion window in packets, aka ssthresh.
   QuicTcpCongestionWindow slowstart_threshold_;
 
+  // Slow start threshold before the last loss event or RTO.
+  QuicTcpCongestionWindow previous_slowstart_threshold_;
+
   // Whether the last loss event caused us to exit slowstart.
   // Used for stats collection of slowstart_packets_lost
   bool last_cutback_exited_slowstart_;
 
   // Maximum number of outstanding packets for tcp.
   QuicTcpCongestionWindow max_tcp_congestion_window_;
 
   DISALLOW_COPY_AND_ASSIGN(TcpCubicSender);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_CONGESTION_CONTROL_TCP_CUBIC_SENDER_H_