Pass allow_classes to reusable_preparser

R=arv@chromium.org, marja@chromium.org

Review URL: https://codereview.chromium.org/471603004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23206 ce2b1a6d-e550-0410-aec6-3dcde31c8c00