[TIMOB-12748] iOS: webView postLayout fires twice

var win = Ti.UI.createWindow();

var webview = Ti.UI.createWebView({
				url : "http://www.google.com",
				width : 100,
				height : 100,
				top : 300
			});
				
webview.addEventListener("postlayout", function() {
				Ti.API.info("---------------------webview postlayout");
	});
win.add(webview);
win.open();