Disable QUIC v29 and earlier. Protected by FLAGS_quic_disable_pre_30.

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 142 matching lines @@
 bool FLAGS_quic_use_cheap_stateless_rejects = false;
 
 // If true, treat timestamps from SO_TIMESTAMPING as QuicWallTimes rather
 // than QuicTimes.
 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, disables support for QUIC version 29 and earlier.
+bool FLAGS_quic_disable_pre_30 = false;