Don't show the picker button until we know a file can be played.
<rdar://problem/20712003>
Created attachment 251761 [details] Proposed patch.
Comment on attachment 251761 [details] Proposed patch. Nit: it'd be nice if we could pull out the logic in updateStatusDisplay() into something like "isPlayable()", but this is fine as-is.
Created attachment 251770 [details] Patch for landing.
Comment on attachment 251770 [details] Patch for landing. Clearing flags on attachment: 251770 Committed r183417: <http://trac.webkit.org/changeset/183417>