Don't do fuzzing of _IsStringWrapperSafeForDefaultValueOf as it expects a non-smi as its first argument.
Review URL: http://codereview.chromium.org/3109010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5253 ce2b1a6d-e550-0410-aec6-3dcde31c8c00