Convert PatchCache (and related methods) to use types rather than objects/maps.

R=rossberg@chromium.org

Review URL: https://chromiumcodereview.appspot.com/75413002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17847 ce2b1a6d-e550-0410-aec6-3dcde31c8c00