Adding cbr support for Opus

webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h

Index: webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h
diff --git a/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h b/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h
index 3d0483b9ca5bbb12b34b40860c543bf05ccc914d..cfbce10de6ca39c536958d4fdee5f15dc3920f5a 100644
--- a/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h
+++ b/webrtc/modules/audio_coding/codecs/opus/audio_encoder_opus.h
@@ -56,6 +56,7 @@ class AudioEncoderOpus final : public AudioEncoder {
     ApplicationMode application = kVoip;
     rtc::Optional<int> bitrate_bps;  // Unset means to use default value.
     bool fec_enabled = false;
+    bool cbr_enabled = false;
     int max_playback_rate_hz = 48000;
     int complexity = kDefaultComplexity;
     // This value may change in the struct's constructor.
@@ -106,6 +107,10 @@ class AudioEncoderOpus final : public AudioEncoder {
   bool SetDtx(bool enable) override;
   bool GetDtx() const override;
 
+  // Set Opus CBR.
+  bool SetCbr(bool enable) override;
+  bool GetCbr() const override;
+
   bool SetApplication(Application application) override;
   void SetMaxPlaybackRate(int frequency_hz) override;
   bool EnableAudioNetworkAdaptor(const std::string& config_string,