nsISupports* ObjectAt(PRInt32 aIndex) const { return NS_STATIC_CAST(nsISupports*, mArray.ElementAt(aIndex));
T* ObjectAt(PRInt32 aIndex) const { return NS_STATIC_CAST(T*,nsCOMArray_base::ObjectAt(aIndex));
    nsISupports* ObjectAt(PRInt32 aIndex) const {        return NS_STATIC_CAST(nsISupports*, mArray.ElementAt(aIndex));    }