Subtitle, caption, and description text tracks are only shown when "the user has indicated an interest" in having them enabled. Add settings for each so WebCore can know when it is appropriate to enable these track types. http://www.whatwg.org/specs/web-apps/current-work/multipage/the-video-element.html#sourcing-out-of-band-text-tracks
<rdar://problem/10501513>
Created attachment 117095 [details] Proposed patch
http://trac.webkit.org/changeset/101674