Make OverheadObserver::OnOverheadChanged count RTP headers only

webrtc/modules/congestion_controller/transport_feedback_adapter.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 31 matching lines @@
   // TODO(holmer): This method should return DelayBasedBwe::Result so that we
   // can get rid of the dependency on BitrateController. Requires changes
   // to the CongestionController interface.
   void OnTransportFeedback(const rtcp::TransportFeedback& feedback) override;
   std::vector<PacketInfo> GetTransportFeedbackVector() const override;
 
   // Implements CallStatsObserver.
   void OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) override;
 
   void SetMinBitrate(int min_bitrate_bps);
+  void SetTransportOverhead(int transport_overhead_bytes_per_packet);
 
   int64_t GetProbingIntervalMs() const;
 
  private:
   std::vector<PacketInfo> GetPacketFeedbackVector(
       const rtcp::TransportFeedback& feedback);
 
   rtc::CriticalSection lock_;
   rtc::CriticalSection bwe_lock_;
+  int transport_overhead_bytes_per_packet_ GUARDED_BY(&lock_);
   SendTimeHistory send_time_history_ GUARDED_BY(&lock_);
   std::unique_ptr<DelayBasedBwe> delay_based_bwe_ GUARDED_BY(&bwe_lock_);
   Clock* const clock_;
   int64_t current_offset_ms_;
   int64_t last_timestamp_us_;
   BitrateController* const bitrate_controller_;
   std::vector<PacketInfo> last_packet_feedback_vector_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_TRANSPORT_FEEDBACK_ADAPTER_H_