Revert r20974: Unify and simplify the FastCloneShallowArrayStub

Due to Layout test redness.

TBR=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/256873007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21007 ce2b1a6d-e550-0410-aec6-3dcde31c8c00