Bug 1715786 - Observe dynamic changes to the ScrollToClick system pref. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D119684

widget/cocoa/nsLookAndFeel.mm

@@ -624,6 +624,12 @@ bool nsLookAndFeel::NativeGetFont(FontID aID, nsString& aFontName, gfxFontStyle&
                     name:@"AppleAquaScrollBarVariantChanged"
                   object:nil
       suspensionBehavior:NSNotificationSuspensionBehaviorDeliverImmediately];
+  [NSDistributedNotificationCenter.defaultCenter
+             addObserver:self
+                selector:@selector(cachedValuesChanged)
+                    name:@"AppleNoRedisplayAppearancePreferenceChanged"
+                  object:nil
+      suspensionBehavior:NSNotificationSuspensionBehaviorCoalesce];
   [NSDistributedNotificationCenter.defaultCenter
              addObserver:self
                 selector:@selector(cachedValuesChanged)