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

net/quic/congestion_control/tcp_cubic_sender.h

Index: net/quic/congestion_control/tcp_cubic_sender.h
diff --git a/net/quic/congestion_control/tcp_cubic_sender.h b/net/quic/congestion_control/tcp_cubic_sender.h
index f9234c92dcc0e7a5e1c8b605fe695aacb4de34a1..8b5083ec92e04c80d9faf256d857f6dd96859169 100644
--- a/net/quic/congestion_control/tcp_cubic_sender.h
+++ b/net/quic/congestion_control/tcp_cubic_sender.h
@@ -54,6 +54,7 @@ class NET_EXPORT_PRIVATE TcpCubicSender : public SendAlgorithmInterface {
                             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,
@@ -118,9 +119,15 @@ class NET_EXPORT_PRIVATE TcpCubicSender : public SendAlgorithmInterface {
   // 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_;