HOuterContext can be expressed in terms of HLoadNamedField.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/131513015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18867 ce2b1a6d-e550-0410-aec6-3dcde31c8c00