Adding cbr support for Opus

webrtc/media/base/mediaconstants.cc

Index: webrtc/media/base/mediaconstants.cc
diff --git a/webrtc/media/base/mediaconstants.cc b/webrtc/media/base/mediaconstants.cc
index 0d8512b9f320a82ff8b04a3d7d29938310fd9ade..7e45bfee8ffc65e115388a0567a9e9f4f34af695 100644
--- a/webrtc/media/base/mediaconstants.cc
+++ b/webrtc/media/base/mediaconstants.cc
@@ -53,6 +53,7 @@ const char kCodecParamSPropStereo[] = "sprop-stereo";
 const char kCodecParamStereo[] = "stereo";
 const char kCodecParamUseInbandFec[] = "useinbandfec";
 const char kCodecParamUseDtx[] = "usedtx";
+const char kCodecParamUseCbr[] = "cbr";
 const char kCodecParamMaxAverageBitrate[] = "maxaveragebitrate";
 const char kCodecParamMaxPlaybackRate[] = "maxplaybackrate";
 
@@ -68,6 +69,7 @@ const int kOpusDefaultMinPTime = 3;
 const int kOpusDefaultSPropStereo = 0;
 const int kOpusDefaultStereo = 0;
 const int kOpusDefaultUseInbandFec = 0;
+const int kOpusDefaultUseCbr = 0;
 const int kOpusDefaultUseDtx = 0;
 const int kOpusDefaultMaxPlaybackRate = 48000;