Replace QUIC's PathMtuAckListener with a non-AckListener approach. Protected by FLAGS_quic_no_mtu_d…

net/quic/quic_sent_packet_manager.cc

 // Copyright 2013 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_sent_packet_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 75 matching lines @@
       consecutive_rto_count_(0),
       consecutive_tlp_count_(0),
       consecutive_crypto_retransmission_count_(0),
       pending_timer_transmission_count_(0),
       max_tail_loss_probes_(kDefaultMaxTailLossProbes),
       enable_half_rtt_tail_loss_probe_(false),
       using_pacing_(false),
       use_new_rto_(false),
       undo_pending_retransmits_(false),
       largest_newly_acked_(0),
+      largest_mtu_acked_(0),
       handshake_confirmed_(false) {}
 
 QuicSentPacketManager::~QuicSentPacketManager() {}
 
 void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) {
   if (config.HasReceivedInitialRoundTripTimeUs() &&
       config.ReceivedInitialRoundTripTimeUs() > 0) {
     rtt_stats_.set_initial_rtt_us(
         max(kMinInitialRoundTripTimeUs,
             min(kMaxInitialRoundTripTimeUs,
@@ skipping 416 matching lines @@
     // transmission of a crypto packet is in flight at once.
     // TODO(ianswett): Instead of handling all crypto packets special,
     // only handle nullptr encrypted packets in a special way.
     const TransmissionInfo& newest_transmission_info =
         unacked_packets_.GetTransmissionInfo(newest_transmission);
     if (HasCryptoHandshake(newest_transmission_info)) {
       unacked_packets_.RemoveFromInFlight(newest_transmission);
     }
   }
 
+  if (FLAGS_quic_no_mtu_discovery_ack_listener &&
+      network_change_visitor_ != nullptr &&
+      info->bytes_sent > largest_mtu_acked_) {
+    largest_mtu_acked_ = info->bytes_sent;
+    network_change_visitor_->OnPathMtuIncreased(largest_mtu_acked_);
+  }
   unacked_packets_.RemoveFromInFlight(info);
   unacked_packets_.RemoveRetransmittability(info);
   if (FLAGS_quic_loss_recovery_use_largest_acked) {
     info->is_unackable = true;
   }
 }
 
 bool QuicSentPacketManager::IsUnacked(QuicPathId,
                                       QuicPacketNumber packet_number) const {
   return unacked_packets_.IsUnacked(packet_number);
@@ skipping 467 matching lines @@
 TransmissionInfo* QuicSentPacketManager::GetMutableTransmissionInfo(
     QuicPacketNumber packet_number) {
   return unacked_packets_.GetMutableTransmissionInfo(packet_number);
 }
 
 void QuicSentPacketManager::RemoveObsoletePackets() {
   unacked_packets_.RemoveObsoletePackets();
 }
 
 }  // namespace net