Parse ELNG box in MP4 container

media/formats/mp4/box_reader.h

Index: media/formats/mp4/box_reader.h
diff --git a/media/formats/mp4/box_reader.h b/media/formats/mp4/box_reader.h
index 3fff1919f10530eb667b3bdaa5fdc4ac9713568d..8847c0c002932bc691ed334ab64c192161c1e99e 100644
--- a/media/formats/mp4/box_reader.h
+++ b/media/formats/mp4/box_reader.h
@@ -63,6 +63,9 @@ class MEDIA_EXPORT BufferReader {
 
   bool ReadVec(std::vector<uint8_t>* t, uint64_t count) WARN_UNUSED_RESULT;
 
+  // Read a null-terminated string.
+  bool ReadString(std::string* v) WARN_UNUSED_RESULT;
+
   // These variants read a 4-byte integer of the corresponding signedness and
   // store it in the 8-byte return type.
   bool Read4Into8(uint64_t* v) WARN_UNUSED_RESULT;