TF: Fix windows build (implicit cast between double and int32_t).

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/431963002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22754 ce2b1a6d-e550-0410-aec6-3dcde31c8c00