unless the caller has indicated that pretenuring is desirable.
This is intended to fix http://jsperf.com/scope-lookups/3
Review URL: http://codereview.chromium.org/7210011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8328 ce2b1a6d-e550-0410-aec6-3dcde31c8c00