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

tests/interactive/scrolling.js

@@ -23,7 +23,7 @@ function test() {
     let v = new St.ScrollView();
     vbox.add(v, { expand: true });
 
-    toggle.connect('notify::checked', function () {
+    toggle.connect('notify::checked', () => {
         v.set_policy(toggle.checked ? Gtk.PolicyType.AUTOMATIC
                      : Gtk.PolicyType.NEVER,
                      Gtk.PolicyType.AUTOMATIC);