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 542f4de1afac97704f9c668beac3553bdc4d36e0..24b585bac0f910923db4e1e5f36d80682828ea8b 100644
--- a/media/formats/mp4/box_definitions.h
+++ b/media/formats/mp4/box_definitions.h
@@ -197,6 +197,7 @@ struct MEDIA_EXPORT HandlerReference : Box {
   DECLARE_BOX_METHODS(HandlerReference);
 
   TrackType type;
+  std::string name;
 };
 
 struct MEDIA_EXPORT AVCDecoderConfigurationRecord : Box {
@@ -310,10 +311,13 @@ 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 {