Set actual transport overhead in rtp_rtcp

BUG=webrtc:6557

Review-Url: https://codereview.webrtc.org/2437503004
Cr-Commit-Position: refs/heads/master@{#14968}

webrtc/audio/audio_send_stream.cc

diff --git a/webrtc/audio/audio_send_stream.cc b/webrtc/audio/audio_send_stream.cc
index 7e8e426..fef5b1d 100644
--- a/webrtc/audio/audio_send_stream.cc
+++ b/webrtc/audio/audio_send_stream.cc
@@ -268,6 +268,11 @@
   return config_;
 }
 
+void AudioSendStream::SetTransportOverhead(int transport_overhead_per_packet) {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  channel_proxy_->SetTransportOverhead(transport_overhead_per_packet);
+}
+
 VoiceEngine* AudioSendStream::voice_engine() const {
   internal::AudioState* audio_state =
       static_cast<internal::AudioState*>(audio_state_.get());