R=rossberg@chromium.org
BUG=v8:2240
TEST=str-to-num.js

Review URL: https://chromiumcodereview.appspot.com/10818003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12169 ce2b1a6d-e550-0410-aec6-3dcde31c8c00