Hack representation inference to assume current behavior of float32 loads and stores, which include implicit representation changes.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/576973003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24072 ce2b1a6d-e550-0410-aec6-3dcde31c8c00