When a track element's parent element changes and the old parent was a media element, then the user agent must remove the track element's corresponding text track from the media element's list of text tracks, and then queue a task to fire an event with the name removetrack, that does not bubble and is not cancelable, and that uses the TrackEvent interface, with the track attribute initialized to the text track's TextTrack object, at the media element's textTracks attribute's TextTrackList object. http://dev.w3.org/html5/spec/media-elements.html#sourcing-out-of-band-text-tracks
<rdar://problem/12644119>
*** This bug has been marked as a duplicate of bug 103421 ***