back to EventListener to be able to dynamically specify behavior
on asynchronously enforced VM breakouts.

Review URL: http://codereview.chromium.org/2962007/show

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5063 ce2b1a6d-e550-0410-aec6-3dcde31c8c00