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/appDisplay.js

@@ -505,7 +505,7 @@ var AllView = class AllView extends BaseAppView {
                 opacity: 0,
                 duration: VIEWS_SWITCH_TIME,
                 mode: Clutter.AnimationMode.EASE_OUT_QUAD,
-                onComplete: () => this.opacity = 255
+                onComplete: () => (this.opacity = 255)
             });
 
         if (animationDirection == IconGrid.AnimationDirection.OUT)