Deprecate quic_do_not_migrate_on_old_packet.

net/quic/core/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/core/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 
 #include <algorithm>
@@ skipping 672 matching lines @@
   }
 
   // Only migrate connection to a new peer address if a change is not underway.
   PeerAddressChangeType peer_migration_type =
       QuicUtils::DetermineAddressChangeType(peer_address_,
                                             last_packet_source_address_);
   // Do not migrate connection if the changed address packet is a reordered
   // packet.
   if (active_peer_migration_type_ == NO_CHANGE &&
       peer_migration_type != NO_CHANGE &&
-      (!FLAGS_quic_do_not_migrate_on_old_packet ||
-       header.packet_number > received_packet_manager_.GetLargestObserved())) {
+      header.packet_number > received_packet_manager_.GetLargestObserved()) {
     StartPeerMigration(header.path_id, peer_migration_type);
   }
 
   --stats_.packets_dropped;
   DVLOG(1) << ENDPOINT << "Received packet header: " << header;
   last_header_ = header;
   DCHECK(connected_);
   return true;
 }
 
@@ skipping 1812 matching lines @@
 // the sender and a signaling mechanism -- if the sender uses a
 // different MinRTO, we may get spurious retransmissions. May not have
 // any benefits, but if the delayed ack becomes a significant source
 // of (likely, tail) latency, then consider such a mechanism.
 const QuicTime::Delta QuicConnection::DelayedAckTime() {
   return QuicTime::Delta::FromMilliseconds(
       min(kMaxDelayedAckTimeMs, kMinRetransmissionTimeMs / 2));
 }
 
 }  // namespace net