cleanup: Disambiguate assignments in arrow functions

As arrow functions have an implicit return value, an assignment of
this.foo = bar could have been intended as a this.foo === bar
comparison. To catch those errors, we will disallow these kinds
of assignments unless they are marked explicitly by an extra pair
of parentheses.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/731

js/ui/accessDialog.js

@@ -147,7 +147,7 @@ var AccessDialogDBus = class {
                                       subtitle, body, options);
         dialog.open();
 
-        dialog.connect('closed', () => this._accessDialog = null);
+        dialog.connect('closed', () => (this._accessDialog = null));
 
         this._accessDialog = dialog;
     }