that use JSARRAY_HAS_FAST_ELEMENTS_CHECK a bit safer in the presence
of pixel arrays.
Review URL: http://codereview.chromium.org/159500

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2556 ce2b1a6d-e550-0410-aec6-3dcde31c8c00