left operand.  For non-commutative operations the right operand could
be overwritten with the Smi left operand.

We need better testing of all of these cases.  We will add more test
cases as a separate commit.
Review URL: http://codereview.chromium.org/598059

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3834 ce2b1a6d-e550-0410-aec6-3dcde31c8c00