Remove largest_observed_ from QuicSentPacketManager, since it's also in

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 8fb27170ef3f0af8af05520eb7eb8718cee88b7a..21a4fbcd84b6f16856a8ba4e21e8f2a851baee31 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -78,7 +78,6 @@ QuicSentPacketManager::QuicSentPacketManager(
                                                      congestion_control_type,
                                                      stats)),
       loss_algorithm_(LossDetectionInterface::Create(loss_type)),
-      largest_observed_(0),
       least_packet_awaited_by_peer_(1),
       first_rto_transmission_(0),
       consecutive_rto_count_(0),
@@ -189,10 +188,9 @@ void QuicSentPacketManager::OnIncomingAck(const QuicAckFrame& ack_frame,
   // We rely on delta_time_largest_observed to compute an RTT estimate, so
   // we only update rtt when the largest observed gets acked.
   bool largest_observed_acked = MaybeUpdateRTT(ack_frame, ack_receive_time);
-  if (largest_observed_ < ack_frame.largest_observed) {
-    largest_observed_ = ack_frame.largest_observed;
-    unacked_packets_.IncreaseLargestObserved(largest_observed_);
-  }
+  DCHECK_GE(ack_frame.largest_observed, unacked_packets_.largest_observed());
+  unacked_packets_.IncreaseLargestObserved(ack_frame.largest_observed);
+
   HandleAckForSentPackets(ack_frame);
   InvokeLossDetection(ack_receive_time);
   MaybeInvokeCongestionEvent(largest_observed_acked, bytes_in_flight);
@@ -224,7 +222,7 @@ void QuicSentPacketManager::OnIncomingAck(const QuicAckFrame& ack_frame,
   if (debug_delegate_ != NULL) {
     debug_delegate_->OnIncomingAck(ack_frame,
                                    ack_receive_time,
-                                   largest_observed_,
+                                   unacked_packets_.largest_observed(),
                                    largest_observed_acked,
                                    GetLeastUnackedSentPacket());
   }
@@ -700,7 +698,7 @@ void QuicSentPacketManager::InvokeLossDetection(QuicTime time) {
   SequenceNumberSet lost_packets =
       loss_algorithm_->DetectLostPackets(unacked_packets_,
                                          time,
-                                         largest_observed_,
+                                         unacked_packets_.largest_observed(),
                                          rtt_stats_);
   for (SequenceNumberSet::const_iterator it = lost_packets.begin();
        it != lost_packets.end(); ++it) {