2.) WebShell now implements the new nsIScriptGlobalObjectOwner.
3.) WebShell supports GetInterface to nsIScriptGlobalObject.
4.) Documents no longer carry around a reference to nsIScriptContextOwner. Instead they hold on to a nsIScriptGlobalObject. nsIDocument::GetScriptContextOwner has now become nsIDocument::GetScriptGlobalObject(). Same change to the set methods.