We can't always guarantee that the didFinishLoad will happen before the plugins are created. Move the plugin hit detection to a more reliable spot.
<rdar://problem/13405856>
Let's not move it, let's just call it from more than one place.
(it was designed to allow calling it again later (the plan was on-plugin-creation), and will choose a primary snapshotted plugin then if there isn't already one)
Created attachment 192838 [details] Patch
Committed r145644: <http://trac.webkit.org/changeset/145644>