We currently throw when there is only a getter defined on the
property, but this should only be the case in strict mode.
Review URL: http://codereview.chromium.org/7064027

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8054 ce2b1a6d-e550-0410-aec6-3dcde31c8c00