cleanup: Use arrow notation for anonymous functions

Arrow notation is great, use it consistently through-out the code base
to bind `this` to anonymous functions, replacing the more overbose
Lang.bind(this, function() {}).

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/23

js/portalHelper/main.js

@@ -357,9 +357,9 @@ var WebPortalHelper = new Lang.Class({
         if (top.window != null)
             return;
 
-        top.window = new PortalWindow(this, top.url, top.timestamp, Lang.bind(this, function(result) {
+        top.window = new PortalWindow(this, top.url, top.timestamp, result => {
             this._dbusImpl.emit_signal('Done', new GLib.Variant('(ou)', [top.connection, result]));
-        }));
+        });
     },
 });