Remember when a media engine is not able to play to an external target after firing the 'webkitcurrentplaybacktargetiswirelesschanged' event so we only tell it to play to the target once.
<rdar://problem/21556117>
Created attachment 255701 [details] Proposed patch.
Comment on attachment 255701 [details] Proposed patch. r=me.
Committed r186032: https://trac.webkit.org/r186032