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

net/quic/quic_flags.cc

 // Copyright 2014 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_flags.h"
 
 // If true, it will return as soon as an error is detected while validating
 // CHLO.
 bool FLAGS_use_early_return_when_verifying_chlo = true;
 
@@ skipping 139 matching lines @@
 bool FLAGS_quic_socket_walltimestamps = false;
 
 // If true, default to immediate forward secure once established on the
 // server side, and the IPFS connection option disables this instead of
 // enabling it.
 bool FLAGS_quic_default_immediate_forward_secure = false;
 
 // If true, QUIC respect HTTP2 SETTINGS frame rather than always close the
 // connection.
 bool FLAGS_quic_respect_http2_settings_frame = false;
+
+// Do not use a QuicAckListener in order to confirm a larger Path MTU.
+bool FLAGS_quic_no_mtu_discovery_ack_listener = false;