4.8.10.7 Ready states http://www.whatwg.org/specs/web-apps/current-work/#dfnReturnLink-38 HAVE_FUTURE_DATA (numeric value 3) ..., and the text tracks are ready. ...
<rdar://problem/10464473>
This was fixed by the changes for https://bugs.webkit.org/show_bug.cgi?id=72547