Clean up FFmpeg media formats and switch to using av_get_bits_per_sample_format().

media/filters/ffmpeg_common.h

 // Copyright (c) 2009 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_FILTERS_FFMPEG_COMMON_H_
 #define MEDIA_FILTERS_FFMPEG_COMMON_H_
 
 // Used for FFmpeg error codes.
 #include <cerrno>
 
@@ skipping 13 matching lines @@
 
 // Wraps FFmpeg's av_free() in a class that can be passed as a template argument
 // to scoped_ptr_malloc.
 class ScopedPtrAVFree {
  public:
   inline void operator()(void* x) const {
     av_free(x);
   }
 };
 
-// MediaFormat key identifying the CodecID.
-extern const char kFFmpegCodecID[];
-
 // FFmpeg MIME types.
 namespace mime_type {
 
 extern const char kFFmpegAudio[];
 extern const char kFFmpegVideo[];
 
 }  // namespace mime_type
 
 namespace interface_id {
 
 extern const char kFFmpegDemuxerStream[];
 
 }  // namespace interface_id
 
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_COMMON_H_