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/misc/systemActions.js

@@ -410,7 +410,7 @@ const SystemActions = new Lang.Class({
         if (Main.screenShield)
             Main.screenShield.lock(false);
 
-        Clutter.threads_add_repaint_func_full(Clutter.RepaintFlags.POST_PAINT, function() {
+        Clutter.threads_add_repaint_func_full(Clutter.RepaintFlags.POST_PAINT, () => {
             Gdm.goto_login_session_sync(null);
             return false;
         });