Implement reading of media track info from WebM and MP4 containers

media/formats/mp4/box_definitions.h

Index: media/formats/mp4/box_definitions.h
diff --git a/media/formats/mp4/box_definitions.h b/media/formats/mp4/box_definitions.h
index e6a62bbace4fc666bd0a5ad081b2c33d45035495..02ae2871535d7b47b7c3602d67cdc20ed0b3eec2 100644
--- a/media/formats/mp4/box_definitions.h
+++ b/media/formats/mp4/box_definitions.h
@@ -163,6 +163,7 @@ struct MEDIA_EXPORT HandlerReference : Box {
   DECLARE_BOX_METHODS(HandlerReference);
 
   TrackType type;
+  std::string name;
 };
 
 struct MEDIA_EXPORT AVCDecoderConfigurationRecord : Box {
@@ -276,10 +277,13 @@ struct MEDIA_EXPORT SampleTable : Box {
 struct MEDIA_EXPORT MediaHeader : Box {
   DECLARE_BOX_METHODS(MediaHeader);
 
+  std::string language() const;
+
   uint64_t creation_time;
   uint64_t modification_time;
   uint32_t timescale;
   uint64_t duration;
+  uint16_t language_code;
 };
 
 struct MEDIA_EXPORT MediaInformation : Box {