Load the arguments object from the context if there are no extensions
objects on the way. Then load the argument with a keyed load ic.

Review URL: http://codereview.chromium.org/2033004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4633 ce2b1a6d-e550-0410-aec6-3dcde31c8c00