Change the QUIC TLP to send new data instead of retransmitting old data

net/quic/quic_connection.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/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 #include <algorithm>
 #include <iterator>
@@ skipping 1585 matching lines @@
   packet_generator_.SetShouldSendAck(send_feedback,
                                      version() > QUIC_VERSION_15);
 }
 
 void QuicConnection::OnRetransmissionTimeout() {
   if (!sent_packet_manager_.HasUnackedPackets()) {
     return;
   }
 
   sent_packet_manager_.OnRetransmissionTimeout();
+  WriteIfNotBlocked();
+  // In the TLP case, the SentPacketManager gives the connection the opportunity
+  // to send new data before retransmitting.
+  if (sent_packet_manager_.MaybeRetransmitTailLossProbe()) {
+    // Send the pending retransmission now that it's been queued.
+    WriteIfNotBlocked();
+  }
 
-  WriteIfNotBlocked();
-
-  // Ensure the retransmission alarm is always set if there are unacked packets.
+  // Ensure the retransmission alarm is always set if there are unacked packets
+  // and nothing waiting to be sent.
   if (!HasQueuedData() && !retransmission_alarm_->IsSet()) {
     QuicTime rto_timeout = sent_packet_manager_.GetRetransmissionTime();
     if (rto_timeout != QuicTime::Zero()) {
       retransmission_alarm_->Set(rto_timeout);
     }
   }
 }
 
 void QuicConnection::SetEncrypter(EncryptionLevel level,
                                   QuicEncrypter* encrypter) {
@@ skipping 336 matching lines @@
   // If we changed the generator's batch state, restore original batch state.
   if (!already_in_batch_mode_) {
     DVLOG(1) << "Leaving Batch Mode.";
     connection_->packet_generator_.FinishBatchOperations();
   }
   DCHECK_EQ(already_in_batch_mode_,
             connection_->packet_generator_.InBatchMode());
 }
 
 }  // namespace net