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/audioDeviceSelection.js

@@ -161,7 +161,7 @@ var AudioDeviceSelectionDBus = class AudioDeviceSelectionDBus {
 
         let [deviceNames] = params;
         let devices = 0;
-        deviceNames.forEach(n => devices |= AudioDevice[n.toUpperCase()]);
+        deviceNames.forEach(n => (devices |= AudioDevice[n.toUpperCase()]));
 
         let dialog;
         try {