Change the QUIC CongestionMap to be based on a vector.

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 c592e133a2c99892ae72119de8fe85efd0185618..a29e69cee9ee28cac28c4b2521dd5052d9093543 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -270,6 +270,10 @@ void QuicSentPacketManager::HandleAckForSentPackets(
     }
 
     if (ContainsKey(ack_frame.missing_packets, sequence_number)) {
+      // Don't continue to increase the nack count for packets not in flight.
+      if (!it->in_flight) {
+        continue;
+      }
       // Consider it multiple nacks when there is a gap between the missing
       // packet and the largest observed, since the purpose of a nack
       // threshold is to tolerate re-ordering.  This handles both StretchAcks
@@ -288,7 +292,7 @@ void QuicSentPacketManager::HandleAckForSentPackets(
     // If data is associated with the most recent transmission of this
     // packet, then inform the caller.
     if (it->in_flight) {
-      packets_acked_[sequence_number] = *it;
+      packets_acked_.push_back(make_pair(sequence_number, *it));
     }
     MarkPacketHandled(sequence_number, *it, delta_largest_observed);
   }
@@ -689,7 +693,7 @@ void QuicSentPacketManager::InvokeLossDetection(QuicTime time) {
     // should be recorded as a loss to the send algorithm, but not retransmitted
     // until it's known whether the FEC packet arrived.
     ++stats_->packets_lost;
-    packets_lost_[sequence_number] = transmission_info;
+    packets_lost_.push_back(make_pair(sequence_number, transmission_info));
     DVLOG(1) << ENDPOINT << "Lost packet " << sequence_number;
 
     if (transmission_info.retransmittable_frames != NULL) {