We have been working on implementing constructors of Events. WebKitAnimationEvent has a constructor in JSC (https://bugs.webkit.org/show_bug.cgi?id=67825), but do not have it in V8.
Created attachment 107023 [details] Patch
Comment on attachment 107023 [details] Patch Clearing flags on attachment: 107023 Committed r94953: <http://trac.webkit.org/changeset/94953>
All reviewed patches have been landed. Closing bug.