Tiny cleanup.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/247953003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20925 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Convert function.prototype to API-style accessor.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/246693005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20926 ce2b1a6d-e550-0410-aec6-3dcde31c8c00