Add support for avc3 codec string.

media/mp4/box_definitions.h

 // Copyright (c) 2012 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_MP4_BOX_DEFINITIONS_H_
 #define MEDIA_MP4_BOX_DEFINITIONS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 165 matching lines @@
   FourCC format;
   uint16 data_reference_index;
   uint16 width;
   uint16 height;
 
   PixelAspectRatioBox pixel_aspect;
   ProtectionSchemeInfo sinf;
 
   // Currently expected to be present regardless of format.
   AVCDecoderConfigurationRecord avcc;
+
+  bool IsFormatValid() const;
 };
 
 struct MEDIA_EXPORT ElementaryStreamDescriptor : Box {
   DECLARE_BOX_METHODS(ElementaryStreamDescriptor);
 
   uint8 object_type;
   AAC aac;
 };
 
 struct MEDIA_EXPORT AudioSampleEntry : Box {
@@ skipping 146 matching lines @@
   std::vector<TrackFragment> tracks;
   std::vector<ProtectionSystemSpecificHeader> pssh;
 };
 
 #undef DECLARE_BOX
 
 }  // namespace mp4
 }  // namespace media
 
 #endif  // MEDIA_MP4_BOX_DEFINITIONS_H_