Minimize the delegate dependencies for non persistent notifications.

chrome/browser/notifications/persistent_notification_handler.cc

 // Copyright 2016 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.
 
 #include "chrome/browser/notifications/persistent_notification_handler.h"
 
 #include "base/logging.h"
 #include "chrome/browser/notifications/platform_notification_service_impl.h"
 #include "chrome/browser/profiles/profile.h"
 
@@ skipping 23 matching lines @@
   const GURL notification_origin(origin);
   DCHECK(notification_origin.is_valid());
 
   PlatformNotificationServiceImpl::GetInstance()->OnPersistentNotificationClick(
       profile, notification_id, notification_origin, action_index, reply);
 }
 
 void PersistentNotificationHandler::OpenSettings(Profile* profile) {
   NotificationCommon::OpenNotificationSettings(profile);
 }
-
-void PersistentNotificationHandler::RegisterNotification(
-    const std::string& notification_id,
-    NotificationDelegate* delegate) {
-  // Nothing to do here since there is no state kept.
-}