Move media::AudioCodec to its own source file

media/base/audio_codecs.h

Index: media/base/audio_codecs.h
diff --git a/media/base/audio_codecs.h b/media/base/audio_codecs.h
new file mode 100644
index 0000000000000000000000000000000000000000..5cba02955bf5e1511a42130ba888c1bfabccceeb
--- /dev/null
+++ b/media/base/audio_codecs.h
@@ -0,0 +1,48 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_BASE_AUDIO_CODECS_H_
+#define MEDIA_BASE_AUDIO_CODECS_H_
+
+#include <string>
+#include "media/base/media_export.h"
+
+namespace media {
+
+enum AudioCodec {
+  // These values are histogrammed over time; do not change their ordinal
+  // values.  When deleting a codec replace it with a dummy value; when adding a
+  // codec, do so at the bottom before kAudioCodecMax, and update the value of
+  // kAudioCodecMax to equal the new codec.
+  kUnknownAudioCodec = 0,
+  kCodecAAC = 1,
+  kCodecMP3 = 2,
+  kCodecPCM = 3,
+  kCodecVorbis = 4,
+  kCodecFLAC = 5,
+  kCodecAMR_NB = 6,
+  kCodecAMR_WB = 7,
+  kCodecPCM_MULAW = 8,
+  kCodecGSM_MS = 9,
+  kCodecPCM_S16BE = 10,
+  kCodecPCM_S24BE = 11,
+  kCodecOpus = 12,
+  kCodecEAC3 = 13,
+  kCodecPCM_ALAW = 14,
+  kCodecALAC = 15,
+  kCodecAC3 = 16,
+  // 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.
+
+  // Must always be equal to the largest entry ever logged.
+  kAudioCodecMax = kCodecAC3,
+};
+
+std::string MEDIA_EXPORT GetCodecName(AudioCodec codec);
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_CODECS_H_