Remove unused method in the native display service

chrome/browser/notifications/native_notification_display_service.h

Index: chrome/browser/notifications/native_notification_display_service.h
diff --git a/chrome/browser/notifications/native_notification_display_service.h b/chrome/browser/notifications/native_notification_display_service.h
index b02bac986c490cf01947d7266e96a70f3ca2bec9..0ba2220f8739cc0bcae3dca93e64f1ae3f83ba30 100644
--- a/chrome/browser/notifications/native_notification_display_service.h
+++ b/chrome/browser/notifications/native_notification_display_service.h
@@ -56,10 +56,6 @@ class NativeNotificationDisplayService : public NotificationDisplayService {
   // for |notification_type|.
   void AddNotificationHandler(NotificationCommon::Type notification_type,
                               std::unique_ptr<NotificationHandler> handler);
-
-  // Removes an implementation added via |AddNotificationHandler|.
-  void RemoveNotificationHandler(NotificationCommon::Type notification_type);
-
  private:
   NotificationHandler* GetNotificationHandler(
       NotificationCommon::Type notification_type);