MIPS: Require smi for keyed store to smi.
MIPS: Require smi for keyed store to smi.

Port r14779 (33d24080)

BUG=

Review URL: https://codereview.chromium.org/15889007

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@14787 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh