Minimize the delegate dependencies for non persistent notifications.

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

 // 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.
 
 #include "chrome/browser/extensions/api/notifications/extension_notification_handler.h"
 
 #include "base/logging.h"
 #include "base/strings/nullable_string16.h"
 #include "base/strings/string_piece.h"
 #include "chrome/browser/extensions/api/notifications/extension_notification_display_helper.h"
@@ skipping 78 matching lines @@
 
   SendEvent(profile, extension_id, histogram_value, event_name,
             EventRouter::USER_GESTURE_ENABLED, std::move(args));
 }
 
 void ExtensionNotificationHandler::OpenSettings(Profile* profile) {
   // Extension notifications don't display a settings button.
   NOTREACHED();
 }
 
-void ExtensionNotificationHandler::RegisterNotification(
-    const std::string& notification_id,
-    NotificationDelegate* delegate) {}
-
 void ExtensionNotificationHandler::SendEvent(
     Profile* profile,
     const std::string& extension_id,
     events::HistogramValue histogram_value,
     const std::string& event_name,
     EventRouter::UserGestureState user_gesture,
     std::unique_ptr<base::ListValue> args) {
   if (extension_id.empty())
     return;
 
   EventRouter* event_router = EventRouter::Get(profile);
   if (!event_router)
     return;
 
   std::unique_ptr<Event> event(
       new Event(histogram_value, event_name, std::move(args)));
   event->user_gesture = user_gesture;
   event_router->DispatchEventToExtension(extension_id, std::move(event));
 }
 
 }  // namespace extensions