Initial CL for the timed text support:
- Add support for MP4 timed text
- Add API for app to turn on/off a text track
- Add timed text metadata(language) in the MediaMetadataRetriever

Change-Id: I0055beba38ac761627dbcc6d581ae9582d68bb94
diff --git a/include/media/mediametadataretriever.h b/include/media/mediametadataretriever.h
index 3e343e0..28f305d 100644
--- a/include/media/mediametadataretriever.h
+++ b/include/media/mediametadataretriever.h
@@ -52,6 +52,7 @@
     METADATA_KEY_VIDEO_WIDTH     = 18,
     METADATA_KEY_VIDEO_HEIGHT    = 19,
     METADATA_KEY_BITRATE         = 20,
+    METADATA_KEY_TIMED_TEXT_LANGUAGES      = 21,
 
     // Add more here...
 };