Calls to a non-global variable would go through the "call to a global"
path, rather than the "call to an arbitrary (other) expression" path.

Review URL: http://codereview.chromium.org/355009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3204 ce2b1a6d-e550-0410-aec6-3dcde31c8c00