code: function(postmessage) {
  			var iframes = document.querySelectorAll("iframe");
  			Array.forEach(iframes, function(iframe) {
  				iframe.contentWindow.postMessage(postmessage, '*');
  			});
  		}
docs: Propagate broadcast to sub documents.
  TODO: implement something similar to {gui.IframeSpirit._postbox}
  but without expecting the bundle gui-spirits@wunderbyte.com
  (it would in that case involve onload instead of onspiritualized)
  @param {string} postmessage