No functional change. Minor change to reorder when the list of QuicAckListeners is swapped into th…

net/quic/quic_unacked_packet_map.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_unacked_packet_map.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "net/quic/quic_connection_stats.h"
 #include "net/quic/quic_flags.h"
@@ skipping 33 matching lines @@
   LOG_IF(DFATAL, largest_sent_packet_ >= packet_number) << packet_number;
   DCHECK_GE(packet_number, least_unacked_ + unacked_packets_.size());
   while (least_unacked_ + unacked_packets_.size() < packet_number) {
     unacked_packets_.push_back(TransmissionInfo());
     unacked_packets_.back().is_unackable = true;
   }
 
   TransmissionInfo info(packet->retransmittable_frames,
                         packet->packet_number_length, transmission_type,
                         sent_time, bytes_sent, packet->is_fec_packet);
-  if (old_packet_number == 0) {
-    if (packet->retransmittable_frames != nullptr &&
-        packet->retransmittable_frames->HasCryptoHandshake() == IS_HANDSHAKE) {
-      ++pending_crypto_packet_count_;
-    }
-    info.ack_listeners.swap(packet->listeners);
-  } else {
+  if (old_packet_number > 0) {
     TransferRetransmissionInfo(old_packet_number, packet_number,
                                transmission_type, &info);
   }
 
   largest_sent_packet_ = packet_number;
   if (set_in_flight) {
     bytes_in_flight_ += bytes_sent;
     info.in_flight = true;
   }
   unacked_packets_.push_back(info);
+  // Swap the ack listeners after to avoid an extra list allocation.
+  // TODO(ianswett): Could use emplace_back when Chromium can.
+  if (old_packet_number == 0) {
+    if (packet->retransmittable_frames != nullptr &&
+        packet->retransmittable_frames->HasCryptoHandshake() == IS_HANDSHAKE) {
+      ++pending_crypto_packet_count_;
+    }
+    unacked_packets_.back().ack_listeners.swap(packet->listeners);
+  }
 }
 
 void QuicUnackedPacketMap::RemoveObsoletePackets() {
   while (!unacked_packets_.empty()) {
     if (!IsPacketUseless(least_unacked_, unacked_packets_.front())) {
       break;
     }
 
     unacked_packets_.pop_front();
     ++least_unacked_;
@@ skipping 281 matching lines @@
     }
   }
   return false;
 }
 
 QuicPacketNumber QuicUnackedPacketMap::GetLeastUnacked() const {
   return least_unacked_;
 }
 
 }  // namespace net