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/components/networkAgent.js

@@ -624,7 +624,7 @@ var NetworkAgent = class {
         this._pluginDir = Gio.file_new_for_path(Config.VPNDIR);
         try {
             let monitor = this._pluginDir.monitor(Gio.FileMonitorFlags.NONE, null);
-            monitor.connect('changed', () => this._vpnCacheBuilt = false);
+            monitor.connect('changed', () => (this._vpnCacheBuilt = false));
         } catch (e) {
             log(`Failed to create monitor for VPN plugin dir: ${e.message}`);
         }