Update smoothed bitrate.

webrtc/modules/audio_coding/acm2/audio_coding_module.cc

Index: webrtc/modules/audio_coding/acm2/audio_coding_module.cc
diff --git a/webrtc/modules/audio_coding/acm2/audio_coding_module.cc b/webrtc/modules/audio_coding/acm2/audio_coding_module.cc
index fe3b252381fef84069303f04c481bf48edda29f0..a3cb287d02f4515f4a106243a6d228a8f7e49d27 100644
--- a/webrtc/modules/audio_coding/acm2/audio_coding_module.cc
+++ b/webrtc/modules/audio_coding/acm2/audio_coding_module.cc
@@ -648,7 +648,8 @@ int AudioCodingModuleImpl::SendFrequency() const {
 void AudioCodingModuleImpl::SetBitRate(int bitrate_bps) {
   rtc::CritScope lock(&acm_crit_sect_);
   if (encoder_stack_) {
-    encoder_stack_->OnReceivedTargetAudioBitrate(bitrate_bps);
+    encoder_stack_->OnReceivedTargetAudioBitrate(bitrate_bps,
+                                                 rtc::Optional<int64_t>());
   }
 }