http://code.google.com/p/v8/issues/detail?id=186

The issue is that the extension object is a normal javascript object
on which assignments to __proto__ changes the prototype chain.
Review URL: http://codereview.chromium.org/18221

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1069 ce2b1a6d-e550-0410-aec6-3dcde31c8c00