Avoid leaking objects between isolated worlds via attribute event listeners

Source/modules/notifications/Notification.h

Index: Source/modules/notifications/Notification.h
diff --git a/Source/modules/notifications/Notification.h b/Source/modules/notifications/Notification.h
index 7717c668dcaecff5a1dbedea95309583418ced19..2b85a1dcc3185c8887935e4d57026943a6ec7a96 100644
--- a/Source/modules/notifications/Notification.h
+++ b/Source/modules/notifications/Notification.h
@@ -115,8 +115,7 @@ public:
     TextDirection direction() const { return dir() == "rtl" ? RTL : LTR; }
 
 #if ENABLE(LEGACY_NOTIFICATIONS)
-    EventListener* ondisplay() { return getAttributeEventListener(eventNames().showEvent); }
-    void setOndisplay(PassRefPtr<EventListener> listener) { setAttributeEventListener(eventNames().showEvent, listener); }
+    DEFINE_MAPPED_ATTRIBUTE_EVENT_LISTENER(display, show);
 #endif
     DEFINE_ATTRIBUTE_EVENT_LISTENER(show);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(error);