Add Opus decode wrapper to media.

media/base/audio_decoder_config.h

Index: media/base/audio_decoder_config.h
diff --git a/media/base/audio_decoder_config.h b/media/base/audio_decoder_config.h
index ce62eb85a1f6389d3fdac77866eeba19200e1279..221e49c828ecddb24ddbf8dff37b7b99d758bb00 100644
--- a/media/base/audio_decoder_config.h
+++ b/media/base/audio_decoder_config.h
@@ -21,21 +21,20 @@ enum AudioCodec {
   kCodecMP3,
   kCodecPCM,
   kCodecVorbis,
-  // ChromiumOS and ChromeOS specific codecs.
   kCodecFLAC,
-  // ChromeOS specific codecs.
   kCodecAMR_NB,
   kCodecAMR_WB,
   kCodecPCM_MULAW,
   kCodecGSM_MS,
   kCodecPCM_S16BE,
   kCodecPCM_S24BE,
+  kCodecOpus,
   // DO NOT ADD RANDOM AUDIO CODECS!
   //
   // The only acceptable time to add a new codec is if there is production code
   // that uses said codec in the same CL.
 
-  kAudioCodecMax = kCodecPCM_S24BE  // Must equal the last "real" codec above.
+  kAudioCodecMax = kCodecOpus  // Must equal the last "real" codec above.
 };
 
 // TODO(dalecurtis): FFmpeg API uses |bytes_per_channel| instead of