Minor change of QUIC's RTO behavior to not change the congestion window

net/quic/quic_sent_packet_manager.cc

Index: net/quic/quic_sent_packet_manager.cc
diff --git a/net/quic/quic_sent_packet_manager.cc b/net/quic/quic_sent_packet_manager.cc
index 770d6ca2d09e6d76518f6256b409a5e0da101b96..7951e62f14aba90826978317f201336f9fe6c47d 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -567,8 +567,6 @@ void QuicSentPacketManager::OnPacketSent(
 }
 
 void QuicSentPacketManager::OnRetransmissionTimeout() {
-  ++consecutive_rto_count_;
-  send_algorithm_->OnRetransmissionTimeout();
   // Abandon all pending packets to ensure the congestion window
   // opens up before we attempt to retransmit packets.
   for (SequenceNumberSet::const_iterator it = pending_packets_.begin();
@@ -587,12 +585,20 @@ void QuicSentPacketManager::OnRetransmissionTimeout() {
            << unacked_packets_.size() << " unacked packets.";
 
   // Retransmit any packet with retransmittable frames.
+  bool packets_retransmitted = false;
   for (UnackedPacketMap::const_iterator it = unacked_packets_.begin();
        it != unacked_packets_.end(); ++it) {
     if (it->second.retransmittable_frames != NULL) {
+      packets_retransmitted = true;
       MarkForRetransmission(it->first, RTO_RETRANSMISSION);
     }
   }
+
+  // Only inform the sent packet manager of an RTO if data was retransmitted.
+  if (packets_retransmitted) {
+    ++consecutive_rto_count_;
+    send_algorithm_->OnRetransmissionTimeout();
+  }
 }
 
 QuicTime QuicSentPacketManager::OnAbandonFecTimeout() {