Simplify QuicSentPacketManager MarkPacketHandled to take an iterator

net/quic/quic_sent_packet_manager.cc

Index: net/quic/quic_sent_packet_manager.cc
diff --git a/net/quic/quic_sent_packet_manager.cc b/net/quic/quic_sent_packet_manager.cc
index eefb320842ad808629f2e5d7bd1cf7faa20cc6ec..ce595610ea5f4bae8e4403e1e5ffa39676836812 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -204,7 +204,7 @@ void QuicSentPacketManager::HandleAckForSentPackets(
     if (it->second.pending) {
       packets_acked_[sequence_number] = it->second;
     }
-    it = MarkPacketHandled(sequence_number, delta_largest_observed);
+    it = MarkPacketHandled(it, delta_largest_observed);
   }
 
   // Discard any retransmittable frames associated with revived packets.
@@ -226,17 +226,6 @@ void QuicSentPacketManager::RetransmitUnackedPackets(
   while (unacked_it != unacked_packets_.end()) {
     const RetransmittableFrames* frames =
         unacked_it->second.retransmittable_frames;
-    // Only mark it as handled if it can't be retransmitted and there are no
-    // pending retransmissions which would be cleared.
-    if (frames == NULL && unacked_it->second.all_transmissions->size() == 1 &&
-        retransmission_type == ALL_PACKETS) {
-      unacked_it = MarkPacketHandled(unacked_it->first,
-                                     QuicTime::Delta::Zero());
-      continue;
-    }
-    // If it had no other transmissions, we handle it above.  If it has
-    // other transmissions, one of them must have retransmittable frames,
-    // so that gets resolved the same way as other retransmissions.
     // TODO(ianswett): Consider adding a new retransmission type which removes
     // all these old packets from unacked and retransmits them as new sequence
     // numbers with no connection to the previous ones.
@@ -343,14 +332,12 @@ void QuicSentPacketManager::MarkPacketRevived(
 }
 
 QuicUnackedPacketMap::const_iterator QuicSentPacketManager::MarkPacketHandled(
-    QuicPacketSequenceNumber sequence_number,
+    QuicUnackedPacketMap::const_iterator it,
     QuicTime::Delta delta_largest_observed) {
-  if (!unacked_packets_.IsUnacked(sequence_number)) {
-    LOG(DFATAL) << "Packet is not unacked: " << sequence_number;
-    return unacked_packets_.end();
-  }
-  const TransmissionInfo& transmission_info =
-      unacked_packets_.GetTransmissionInfo(sequence_number);
+  LOG_IF(DFATAL, it == unacked_packets_.end())
+      << "MarkPacketHandled must be passed a valid iterator entry.";
+  const QuicPacketSequenceNumber sequence_number = it->first;
+  const TransmissionInfo& transmission_info = it->second;
 
   QuicPacketSequenceNumber newest_transmission =
       *transmission_info.all_transmissions->rbegin();