[WebGL] VideoTextureCopierCV doesn't correctly restore vertex attribute state
<rdar://problem/34386621>
Created attachment 320528 [details] Patch
Committed r221933: <http://trac.webkit.org/changeset/221933>
Re-opened since this is blocked by bug 176969
Committed r222198: <http://trac.webkit.org/changeset/222198>