Further cleanup to QuicAckNotifier and QuicAckNotifierManager.

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 357c5469133e19d50abc9fe4133a159143c3609a..73e3c8e1c2ac87692fb8dc1e4256d95c67d7d9f8 100644
--- a/net/quic/quic_ack_notifier_manager.cc
+++ b/net/quic/quic_ack_notifier_manager.cc
@@ -40,12 +40,9 @@ void AckNotifierManager::OnPacketAcked(QuicPacketSequenceNumber sequence_number,
 
   // One or more AckNotifiers are registered as interested in this sequence
   // number. Iterate through them and call OnAck on each.
-  AckNotifierList& ack_notifier_list = map_it->second;
-  for (QuicAckNotifier* ack_notifier : ack_notifier_list) {
-    ack_notifier->OnAck(sequence_number, delta_largest_observed);
-
-    // If this has resulted in an empty AckNotifer, erase it.
-    if (!ack_notifier->HasUnackedPackets()) {
+  for (QuicAckNotifier* ack_notifier : map_it->second) {
+    if (ack_notifier->OnAck(delta_largest_observed)) {
+      // If this has resulted in an empty AckNotifer, erase it.
       delete ack_notifier;
     }
   }
@@ -80,7 +77,9 @@ void AckNotifierManager::OnPacketRetransmitted(
 void AckNotifierManager::OnSerializedPacket(
     const SerializedPacket& serialized_packet) {
   if (FLAGS_quic_attach_ack_notifiers_to_packets) {
-    // Inform each attached AckNotifier of the packet's sequence number.
+    // Inform each attached AckNotifier of the packet's serialization.
+    AckNotifierList& notifier_list =
+        ack_notifier_map_[serialized_packet.sequence_number];
     for (QuicAckNotifier* notifier : serialized_packet.notifiers) {
       if (notifier == nullptr) {
         LOG(DFATAL) << "AckNotifier should not be nullptr.";
@@ -90,7 +89,7 @@ void AckNotifierManager::OnSerializedPacket(
 
       // Update the mapping in the other direction, from sequence number to
       // AckNotifier.
-      ack_notifier_map_[serialized_packet.sequence_number].push_back(notifier);
+      notifier_list.push_back(notifier);
     }
   } else {
     // AckNotifiers can only be attached to retransmittable frames.