BUG=http://code.google.com/p/v8/issues/detail?id=646
TEST=test/mjsunit/regress/regress-646.js
Review URL: http://codereview.chromium.org/1023008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4167 ce2b1a6d-e550-0410-aec6-3dcde31c8c00