In built-in code we use arrays for internal computations. This makes it
possible to affect the built-in code by putting getters or setters on
the array prototype chain. Using internal arrays prevents those issues.

Related to: http://code.google.com/p/v8/source/detail?r=7040

R=svenpanne@chromium.org
TEST=test262/15.4.4.20-9-b-6

Review URL: http://codereview.chromium.org/8353006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9707 ce2b1a6d-e550-0410-aec6-3dcde31c8c00