cleanup: Use Function.prototype.bind()

When not using arrow notation with anonymous functions, we use Lang.bind()
to bind `this` to named callbacks. However since ES5, this functionality
is already provided by Function.prototype.bind() - in fact, Lang.bind()
itself uses it when no extra arguments are specified. Just use the built-in
function directly where possible, and use arrow notation in the few places
where we pass additional arguments.

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

js/ui/status/screencast.js

@@ -17,7 +17,7 @@ var Indicator = new Lang.Class({
         this._indicator.add_style_class_name('screencast-indicator');
         this._sync();
 
-        Main.screencastService.connect('updated', Lang.bind(this, this._sync));
+        Main.screencastService.connect('updated', this._sync.bind(this));
     },
 
     _sync() {