This avoids problems when getters/setters are defined on Object.

BUG=v8:1232


Review URL: http://codereview.chromium.org/6625054

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7081 ce2b1a6d-e550-0410-aec6-3dcde31c8c00