Fix Hydrogen's BuildStore()

BUG=chromium:417508
LOG=y
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/612423002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24366 ce2b1a6d-e550-0410-aec6-3dcde31c8c00