Keyed loads from super with numeric keys.

R=ishell@chromium.org, arv@chromium.org
BUG=v8:3330
LOG=N

Review URL: https://codereview.chromium.org/638193004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24522 ce2b1a6d-e550-0410-aec6-3dcde31c8c00