Add TransportFeedbackPacketLossTracker.

webrtc/modules/rtp_rtcp/source/rtcp_packet/transport_feedback.h

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 28 matching lines @@
   void SetFeedbackSequenceNumber(uint8_t feedback_sequence);
   // NOTE: This method requires increasing sequence numbers (excepting wraps).
   bool AddReceivedPacket(uint16_t sequence_number, int64_t timestamp_us);
 
   enum class StatusSymbol {
     kNotReceived,
     kReceivedSmallDelta,
     kReceivedLargeDelta,
   };
 
-  uint16_t GetBaseSequence() const;
-  std::vector<TransportFeedback::StatusSymbol> GetStatusVector() const;
+  virtual uint16_t GetBaseSequence() const;
+  virtual std::vector<TransportFeedback::StatusSymbol> GetStatusVector() const;
   std::vector<int16_t> GetReceiveDeltas() const;
 
   // Get the reference time in microseconds, including any precision loss.
   int64_t GetBaseTimeUs() const;
   // Convenience method for getting all deltas as microseconds. The first delta
   // is relative the base time.
   std::vector<int64_t> GetReceiveDeltasUs() const;
 
   bool Parse(const CommonHeader& packet);
   static std::unique_ptr<TransportFeedback> ParseFrom(const uint8_t* buffer,
@@ skipping 49 matching lines @@
   uint16_t first_symbol_cardinality_;
   bool vec_needs_two_bit_symbols_;
   uint32_t size_bytes_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(TransportFeedback);
 };
 
 }  // namespace rtcp
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_TRANSPORT_FEEDBACK_H_