Javascript (Greasemonkey) : maximize newly opened windows

Question

I try to code a Greasemonkey javascript snippet to have new windows opened maximized by Firefox.

Here's my code :

// ==UserScript==
// @name        Maximize windows
// @namespace   maxiwin
// @include     http://*.*
// @include     https://*.*
// @version     1
// @grant       none
// ==/UserScript==
if (window.windowState != 1){
  dc = window.getInterface(Components.interfaces.nsIDOMChromeWindow);
  dc.maximize();
}

But it doesn't work. Also tried :

if (window.windowState != 1){
  var domchrome = Components.Constructor("@mozilla.org/nsidomchromewindow;1");
  var dc = new domchrome();
  dc = dc.QueryInterface(Components.interfaces.nsIDOMChromeWindow);
  dc.maximize();
}

It doesn't work either. Does a Greasemonkey specialist have a solution ?