Refactor QuicConnection's async write behavior to record a packet as

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 502 matching lines @@
   return unacked_packets_.GetLeastUnackedSentPacket();
 }
 
 bool QuicSentPacketManager::OnPacketSent(
     QuicPacketSequenceNumber sequence_number,
     QuicTime sent_time,
     QuicByteCount bytes,
     TransmissionType transmission_type,
     HasRetransmittableData has_retransmittable_data) {
   DCHECK_LT(0u, sequence_number);
+  DCHECK(unacked_packets_.IsUnacked(sequence_number));
   LOG_IF(DFATAL, bytes == 0) << "Cannot send empty packets.";
   if (pending_timer_transmission_count_ > 0) {
     --pending_timer_transmission_count_;
   }
-  // In rare circumstances, the packet could be serialized, sent, and then acked
-  // before OnPacketSent is called.
-  if (!unacked_packets_.IsUnacked(sequence_number)) {
-    return false;
-  }
 
   if (unacked_packets_.bytes_in_flight() == 0) {
     // TODO(ianswett): Consider being less aggressive to force a new
     // recent_min_rtt, likely by not discarding a relatively new sample.
     DVLOG(1) << "Sampling a new recent min rtt within 2 samples. currently:"
              << rtt_stats_.recent_min_rtt().ToMilliseconds() << "ms";
     rtt_stats_.SampleNewRecentMinRtt(kNumMinRttSamplesAfterQuiescence);
   }
 
   // Only track packets as in flight that the send algorithm wants us to track.
@@ skipping 348 matching lines @@
 
   // Set up a pacing sender with a 5 millisecond alarm granularity.
   using_pacing_ = true;
   send_algorithm_.reset(
       new PacingSender(send_algorithm_.release(),
                        QuicTime::Delta::FromMilliseconds(5),
                        kInitialUnpacedBurst));
 }
 
 }  // namespace net