Update from https://crrev.com/309415

net/quic/quic_ack_notifier.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_ack_notifier.h"
 
 #include <set>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 50 matching lines @@
   }
   return false;
 }
 
 void QuicAckNotifier::UpdateSequenceNumber(
     QuicPacketSequenceNumber old_sequence_number,
     QuicPacketSequenceNumber new_sequence_number) {
   DCHECK(!ContainsKey(sequence_numbers_, new_sequence_number));
 
   PacketInfo packet_info;
-  hash_map<QuicPacketSequenceNumber, PacketInfo>::iterator it =
-      sequence_numbers_.find(old_sequence_number);
+  auto it = sequence_numbers_.find(old_sequence_number);
   if (it != sequence_numbers_.end()) {
     packet_info = it->second;
     sequence_numbers_.erase(it);
   } else {
     DLOG(DFATAL) << "Old sequence number not found.";
   }
 
   ++retransmitted_packet_count_;
   retransmitted_byte_count_ += packet_info.packet_payload_size;
   sequence_numbers_.insert(make_pair(new_sequence_number, packet_info));
 }
 
 };  // namespace net