Discard old packets from the QuicSentPacketManager which are only

net/quic/quic_unacked_packet_map.cc

Index: net/quic/quic_unacked_packet_map.cc
diff --git a/net/quic/quic_unacked_packet_map.cc b/net/quic/quic_unacked_packet_map.cc
index 7276b139e91bc7f223c40504c98187819a2c93a4..85074dfce46012056fbb193038c85b312fdd3682 100644
--- a/net/quic/quic_unacked_packet_map.cc
+++ b/net/quic/quic_unacked_packet_map.cc
@@ -52,7 +52,7 @@ void QuicUnackedPacketMap::AddPacket(
 
 void QuicUnackedPacketMap::RemoveObsoletePackets() {
   while (!unacked_packets_.empty()) {
-    if (!IsPacketUseless(least_unacked_, unacked_packets_.front())) {
+    if (!IsPacketRemovable(least_unacked_, unacked_packets_.front())) {
       break;
     }
     delete unacked_packets_.front().all_transmissions;
@@ -207,6 +207,16 @@ bool QuicUnackedPacketMap::IsPacketUseless(
       info.all_transmissions == NULL;
 }
 
+bool QuicUnackedPacketMap::IsPacketRemovable(
+    QuicPacketSequenceNumber sequence_number,
+    const TransmissionInfo& info) const {
+  return (sequence_number <= largest_observed_ ||
+          unacked_packets_.size() > kMaxTcpCongestionWindow) &&
+      !info.in_flight &&
+      info.retransmittable_frames == NULL &&
+      info.all_transmissions == NULL;
+}
+
 bool QuicUnackedPacketMap::IsUnacked(
     QuicPacketSequenceNumber sequence_number) const {
   if (sequence_number < least_unacked_ ||