Merged r15015 into trunk branch.

MIPS: Baseline for-of implementation.

BUG=v8:2214

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/16371004

git-svn-id: https://v8.googlecode.com/svn/trunk@15019 ce2b1a6d-e550-0410-aec6-3dcde31c8c00