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/ui/osdWindow.js

@@ -177,10 +177,10 @@ var OsdWindow = new Lang.Class({
                          { opacity: 0,
                            time: FADE_TIME,
                            transition: 'easeOutQuad',
-                           onComplete: Lang.bind(this, function() {
+                           onComplete: () => {
                               this._reset();
                               Meta.enable_unredirect_for_screen(global.screen);
-                           })
+                           }
                          });
         return GLib.SOURCE_REMOVE;
     },