Fixed navbar autohide after viewport resize

lib/persona.js

@@ -3,18 +3,25 @@
 /*globals ajaxify, config, utils, app, socket, NProgress*/
 
 $(document).ready(function() {
-	var env = utils.findBootstrapEnvironment();
+	$(".navbar-fixed-top").autoHidingNavbar({
+		showOnBottom: false,
+		disableAutohide: true
+	});
 
 	setupNProgress();
 	setupTaskbar();
 	setupEditedByIcon();
 	setupMobileMenu();
 	setupQuickReply();
+	updateAutoHidingNavbar();
 
-	if (env === 'xs' || env ==='sm') {
-		$(".navbar-fixed-top").autoHidingNavbar({
-			showOnBottom: false
-		});
+	$(window).on('resize', function() {
+		updateAutoHidingNavbar();
+	});
+
+	function updateAutoHidingNavbar() {
+			var env = utils.findBootstrapEnvironment();
+			$(".navbar-fixed-top").autoHidingNavbar('setDisableAutohide', !(env === 'xs' || env ==='sm'));
 	}
 
 	function setupNProgress() {