Parse ELNG box in MP4 container

media/formats/mp4/box_definitions.cc

Index: media/formats/mp4/box_definitions.cc
diff --git a/media/formats/mp4/box_definitions.cc b/media/formats/mp4/box_definitions.cc
index ced31cc51dbc20dc3b552bc4bea80c259c74a1a6..11688e969b2302c19bccc2e1298efda3833b300c 100644
--- a/media/formats/mp4/box_definitions.cc
+++ b/media/formats/mp4/box_definitions.cc
@@ -776,13 +776,25 @@ bool MediaInformation::Parse(BoxReader* reader) {
          reader->ReadChild(&sample_table);
 }
 
+ExtendedLanguageTag::ExtendedLanguageTag() {}
+ExtendedLanguageTag::~ExtendedLanguageTag() {}
+FourCC ExtendedLanguageTag::BoxType() const {
+  return FOURCC_ELNG;
+}
+
+bool ExtendedLanguageTag::Parse(BoxReader* reader) {
+  RCHECK(reader->ReadFullBoxHeader());
+  RCHECK(reader->ReadString(&language_tag));
+  return true;
+}
+
 Media::Media() {}
 Media::~Media() {}
 FourCC Media::BoxType() const { return FOURCC_MDIA; }
 
 bool Media::Parse(BoxReader* reader) {
-  RCHECK(reader->ScanChildren() &&
-         reader->ReadChild(&header) &&
+  RCHECK(reader->ScanChildren() && reader->ReadChild(&header) &&
+         reader->MaybeReadChild(&extended_language_tag) &&
          reader->ReadChild(&handler));
 
   // Maddeningly, the HandlerReference box specifies how to parse the