FastCloneShallowObjectStub is only called from full code. When the code
is optimized, then we'll inline the cloning and respect pretenure mode.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/104403008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18368 ce2b1a6d-e550-0410-aec6-3dcde31c8c00