Fix bug in QuicSentPacketManager::ClearPreviousRetransmissions where

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 0c63614055b5b5219e85dbec0bf2ab8372b730b0..d46ffb98e170e8f266e9be008fa5ea3d4edf7b15 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -284,30 +284,13 @@ void QuicSentPacketManager::ClearPreviousRetransmissions(size_t num_to_clear) {
   UnackedPacketMap::iterator it = unacked_packets_.begin();
   while (it != unacked_packets_.end() && num_to_clear > 0) {
     QuicPacketSequenceNumber sequence_number = it->first;
-    // If this is not a previous transmission then there is no point
-    // in clearing out any further packets, because it will not affect
-    // the high water mark.
-    SequenceNumberSet* all_transmissions = it->second.all_transmissions;
-    if (all_transmissions->size() == 1) {
-      if (it->second.retransmittable_frames == NULL) {
-        // This is a current transmission, but a previous transmission has
-        // been acked, so it's safe to remove.
-        it = MarkPacketHandled(sequence_number, NOT_RECEIVED_BY_PEER);
-        --num_to_clear;
-        continue;
-      }
-      break;
-    }
-    QuicPacketSequenceNumber newest_transmission = *all_transmissions->rbegin();
-    if (sequence_number == newest_transmission) {
-      break;
-    }
-    if (it->second.pending) {
+    // If this is a pending packet, or has retransmittable data, then there is
+    // no point in clearing out any further packets, because they would not
+    // affect the high water mark.
+    if (it->second.pending || it->second.retransmittable_frames != NULL) {
       break;
     }
 
-    DCHECK(it->second.retransmittable_frames == NULL);
-    DCHECK_LT(1u, all_transmissions->size());
     ++it;
     RemovePacket(sequence_number);
     --num_to_clear;