Array.prototype.values
Array.prototype.keys
Array.prototype.entries

These all return an Array Iterator object which has a next
method.

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-15.4.5

BUG=v8:2722
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/16848004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15620 ce2b1a6d-e550-0410-aec6-3dcde31c8c00