Minimize the delegate dependencies for non persistent notifications.

chrome/browser/extensions/api/notifications/extension_notification_handler.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_NOTIFICATIONS_EXTENSION_NOTIFICATION_HANDLER_H_
 #define CHROME_BROWSER_EXTENSIONS_API_NOTIFICATIONS_EXTENSION_NOTIFICATION_HANDLER_H_
 
 #include "base/macros.h"
 #include "chrome/browser/notifications/notification_handler.h"
 #include "extensions/browser/event_router.h"
@@ skipping 13 matching lines @@
   void OnClose(Profile* profile,
                const std::string& origin,
                const std::string& notification_id,
                bool by_user) override;
   void OnClick(Profile* profile,
                const std::string& origin,
                const std::string& notification_id,
                int action_index,
                const base::NullableString16& reply) override;
   void OpenSettings(Profile* profile) override;
-  void RegisterNotification(const std::string& notification_id,
-                            NotificationDelegate* delegate) override;
 
  protected:
   // Overriden in unit tests.
   virtual void SendEvent(Profile* profile,
                          const std::string& extension_id,
                          events::HistogramValue histogram_value,
                          const std::string& name,
                          EventRouter::UserGestureState user_gesture,
                          std::unique_ptr<base::ListValue> args);
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionNotificationHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_NOTIFICATIONS_EXTENSION_NOTIFICATION_HANDLER_H_