Make OverheadObserver::OnOverheadChanged count RTP headers only

webrtc/voice_engine/channel.h

Index: webrtc/voice_engine/channel.h
diff --git a/webrtc/voice_engine/channel.h b/webrtc/voice_engine/channel.h
index 11e109e3c8c631b46d1261eced1bba665bcb73e6..fca682141d56beb13392cb01d4d642b0199f079d 100644
--- a/webrtc/voice_engine/channel.h
+++ b/webrtc/voice_engine/channel.h
@@ -415,7 +415,7 @@ class Channel
   void SetRtcEventLog(RtcEventLog* event_log);
 
   void SetRtcpRttStats(RtcpRttStats* rtcp_rtt_stats);
-  void SetTransportOverhead(int transport_overhead_per_packet);
+  void SetTransportOverhead(size_t transport_overhead_per_packet);
 
   // From OverheadObserver in the RTP/RTCP module
   void OnOverheadChanged(size_t overhead_bytes_per_packet) override;
@@ -443,6 +443,8 @@ class Channel
                                 RTPExtensionType type,
                                 unsigned char id);
 
+  void UpdateOverheadForEncoder();
+
   int GetRtpTimestampRateHz() const;
   int64_t GetRTT(bool allow_associate_channel) const;
 
@@ -529,6 +531,8 @@ class Channel
   uint32_t _lastLocalTimeStamp;
   int8_t _lastPayloadType;
   bool _includeAudioLevelIndication;
+  size_t transport_overhead_per_packet_;
+  size_t rtp_overhead_per_packet_;
   // VoENetwork
   AudioFrame::SpeechType _outputSpeechType;
   // VoEVideoSync