Update from chromium https://crrev.com/302282

net/quic/quic_received_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_received_packet_manager.h"
 
 #include <limits>
 #include <utility>
 
 #include "base/logging.h"
@@ skipping 266 matching lines @@
       entropy_tracker_.SetCumulativeEntropyUpTo(stop_waiting.least_unacked,
                                                 stop_waiting.entropy_hash);
     }
     peer_least_packet_awaiting_ack_ = stop_waiting.least_unacked;
   }
   DCHECK(ack_frame_.missing_packets.empty() ||
          *ack_frame_.missing_packets.begin() >=
              peer_least_packet_awaiting_ack_);
 }
 
-bool QuicReceivedPacketManager::HasNewMissingPackets() {
+bool QuicReceivedPacketManager::HasNewMissingPackets() const {
   return !ack_frame_.missing_packets.empty() &&
       (ack_frame_.largest_observed -
        *ack_frame_.missing_packets.rbegin()) <= kMaxPacketsAfterNewMissing;
 }
 
+size_t QuicReceivedPacketManager::NumTrackedPackets() const {
+  return entropy_tracker_.size();
+}
+
 }  // namespace net