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 01907d269b1fa2eab5ce5396a1e09f16ce3e326b..a4ba8d7bd253f0ec67d0f5df0278cf5dd9e3dfcb 100644
--- a/webrtc/voice_engine/channel.h
+++ b/webrtc/voice_engine/channel.h
@@ -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;
+  int _transport_overhead_per_packet;
+  int _rtp_overhead_per_packet;
   // VoENetwork
   AudioFrame::SpeechType _outputSpeechType;
   // VoEVideoSync