Adding cbr support for Opus

webrtc/modules/audio_coding/codecs/cng/audio_encoder_cng.cc

Index: webrtc/modules/audio_coding/codecs/cng/audio_encoder_cng.cc
diff --git a/webrtc/modules/audio_coding/codecs/cng/audio_encoder_cng.cc b/webrtc/modules/audio_coding/codecs/cng/audio_encoder_cng.cc
index bcb11eef8b90ce2c02588658812e40c83676a944..066be53ed48b691f8ddf5b14d9c16140a2d48a63 100644
--- a/webrtc/modules/audio_coding/codecs/cng/audio_encoder_cng.cc
+++ b/webrtc/modules/audio_coding/codecs/cng/audio_encoder_cng.cc
@@ -167,6 +167,10 @@ bool AudioEncoderCng::SetFec(bool enable) {
   return speech_encoder_->SetFec(enable);
 }
 
+bool AudioEncoderCng::SetCbr(bool enable) {
+  return speech_encoder_->SetCbr(enable);
+}
+
 bool AudioEncoderCng::SetDtx(bool enable) {
   return speech_encoder_->SetDtx(enable);
 }