--- a/dom/events/EventListenerManager.h
+++ b/dom/events/EventListenerManager.h
@@ -184,39 +184,34 @@ public:
     EventMessage mEventMessage;
 
     enum ListenerType : uint8_t
     {
       eNativeListener = 0,
       eJSEventListener,
       eWrappedJSListener,
       eWebIDLListener,
-      eListenerTypeCount
     };
-    uint8_t mListenerType;
+    ListenerType mListenerType;
 
     bool mListenerIsHandler : 1;
     bool mHandlerIsString : 1;
     bool mAllEvents : 1;
     bool mIsChrome : 1;
 
     EventListenerFlags mFlags;
 
     JSEventHandler* GetJSEventHandler() const
     {
       return (mListenerType == eJSEventListener) ?
         static_cast<JSEventHandler*>(mListener.GetXPCOMCallback()) :
         nullptr;
     }
 
-    Listener()
-    {
-      MOZ_ASSERT(sizeof(mListenerType) == 1);
-      MOZ_ASSERT(eListenerTypeCount < 255);
-    }
+    Listener() = default;
 
     ~Listener()
     {
       if ((mListenerType == eJSEventListener) && mListener) {
         static_cast<JSEventHandler*>(
           mListener.GetXPCOMCallback())->Disconnect();
       }
     }