QUIC - minor clean up of comments per wtc' comments for the CL:

net/quic/quic_sent_packet_manager.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_sent_packet_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 155 matching lines @@
       received_info.delta_time_largest_observed;
   QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
   while (it != unacked_packets_.end()) {
     QuicPacketSequenceNumber sequence_number = it->first;
     if (sequence_number > received_info.largest_observed) {
       // These packets are still in flight.
       break;
     }
 
     if (IsAwaitingPacket(received_info, sequence_number)) {
-      // Remove any packets not being tracked by the send algorithm, allowing
-      // the high water mark to be raised if necessary.
+      // Remove any rtt only packets less than or equal to the largest observed,
+      // since they will not produce an RTT measurement.
       if (QuicUnackedPacketMap::IsForRttOnly(it->second)) {
         it = MarkPacketHandled(sequence_number, delta_largest_observed);
       } else {
         // 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
         // and Forward Acks.
         // The nack count only increases when the largest observed increases.
         size_t min_nacks = received_info.largest_observed - sequence_number;
         // Truncated acks can nack the largest observed, so use a min of 1.
@@ skipping 586 matching lines @@
     return;
   }
 
   using_pacing_ = true;
   send_algorithm_.reset(
       new PacingSender(send_algorithm_.release(),
                        QuicTime::Delta::FromMicroseconds(1)));
 }
 
 }  // namespace net