Replace the map in QuicAckNotifier with a counter.

net/quic/quic_ack_notifier_manager.cc

Index: net/quic/quic_ack_notifier_manager.cc
diff --git a/net/quic/quic_ack_notifier_manager.cc b/net/quic/quic_ack_notifier_manager.cc
index 39db3f2fe48e4a990b336061fbd90390630b9114..0d37752e211ab130f4ffcb9243ecf486e8f9ec1d 100644
--- a/net/quic/quic_ack_notifier_manager.cc
+++ b/net/quic/quic_ack_notifier_manager.cc
@@ -50,9 +50,10 @@ void AckNotifierManager::OnPacketAcked(QuicPacketSequenceNumber sequence_number,
   ack_notifier_map_.erase(map_it);
 }
 
-void AckNotifierManager::UpdateSequenceNumber(
+void AckNotifierManager::OnPacketRetransmitted(
     QuicPacketSequenceNumber old_sequence_number,
-    QuicPacketSequenceNumber new_sequence_number) {
+    QuicPacketSequenceNumber new_sequence_number,
+    int packet_payload_size) {
   auto map_it = ack_notifier_map_.find(old_sequence_number);
   if (map_it == ack_notifier_map_.end()) {
     // No AckNotifiers are interested in the old sequence number.
@@ -62,8 +63,7 @@ void AckNotifierManager::UpdateSequenceNumber(
   // Update the existing QuicAckNotifiers to the new sequence number.
   AckNotifierList& ack_notifier_list = map_it->second;
   for (QuicAckNotifier* ack_notifier : ack_notifier_list) {
-    ack_notifier->UpdateSequenceNumber(old_sequence_number,
-                                       new_sequence_number);
+    ack_notifier->OnPacketRetransmitted(packet_payload_size);
   }
 
   // The old sequence number is no longer of interest, copy the updated