Various extension-related cleanup and simplifications.

Removes the embarrassing "static"s, shuffles some code around, doing various cleanups on the way.

R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/130213009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18659 ce2b1a6d-e550-0410-aec6-3dcde31c8c00