backward jump.  The frame entering the backward block is not used, so
the this is mostly just a bookkeeping change.
Review URL: http://codereview.chromium.org/115464

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1989 ce2b1a6d-e550-0410-aec6-3dcde31c8c00