This will allow us to remove the separate call to IsExternal() from our
chrome client code, speeding up the combination.

Review URL: http://codereview.chromium.org/113035

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1887 ce2b1a6d-e550-0410-aec6-3dcde31c8c00