Revert of Deprecate native and extension notification delegates.

chrome/browser/notifications/web_notification_delegate.h

 // 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.
 
 #ifndef CHROME_BROWSER_NOTIFICATIONS_WEB_NOTIFICATION_DELEGATE_H_
 #define CHROME_BROWSER_NOTIFICATIONS_WEB_NOTIFICATION_DELEGATE_H_
 
 #include <string>
 
 #include "base/feature_list.h"
@@ skipping 16 matching lines @@
   WebNotificationDelegate(NotificationCommon::Type notification_type,
                           Profile* profile,
                           const std::string& notification_id,
                           const GURL& origin);
 
   // NotificationDelegate implementation.
   std::string id() const override;
   bool SettingsClick() override;
   bool ShouldDisplaySettingsButton() override;
   bool ShouldDisplayOverFullscreen() const override;
+  void Display() override;
   void Close(bool by_user) override;
   void Click() override;
   void ButtonClick(int button_index) override;
   void ButtonClickWithReply(int button_index,
                             const base::string16& reply) override;
 
  protected:
   ~WebNotificationDelegate() override;
   const GURL& origin() { return origin_; }
 
  private:
   NotificationCommon::Type notification_type_;
   Profile* profile_;
   std::string notification_id_;
   GURL origin_;
 
   DISALLOW_COPY_AND_ASSIGN(WebNotificationDelegate);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_WEB_NOTIFICATION_DELEGATE_H_