Bugfix in hydrogen array literal code generation.

If an array literal contains some non-constant elements, is of type SMI, and
then the boilerplate transitions to double or fast sometime after we've
crankshafted the code, then we could incorrectly store smis in double arrays.

BUG=
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/17334004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15207 ce2b1a6d-e550-0410-aec6-3dcde31c8c00