code: function() {
  			this._unloaded = true;
  			gui.$shutdown();
  			dobrodcast(gui.BROADCAST_TOUNLOAD, gui.BROADCAST_ONUNLOAD);
  			doaction(gui.ACTION_DOC_UNLOAD, location.href);
  		}
docs: Dispatch `unload` event to hosting document.
  TODO: https://developer.mozilla.org/en-US/docs/Using_Firefox_1.5_caching