How do you programmatically close a browser window when you didn't open it? Of course, everybody knows you can't. If they don't know that, they're novice developers and some seasoned veteran will set them straight... gently or otherwise.
All you need to start the magic is to assign a window to the opener property of the current window. If this attribute is not set, the browser will realize that the current window is not open to your manipulation and nothing will happen.
window.opener = top;