Eliminatable CheckMaps replaced with if(true) or if(false).

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/130613003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18592 ce2b1a6d-e550-0410-aec6-3dcde31c8c00