Revert of Deprecate native and extension notification delegates.

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/feature_list.h"
 #include "base/macros.h"
 #include "chrome/browser/notifications/notification_handler.h"
 #include "extensions/browser/event_router.h"
 
 class Profile;
 
 namespace extensions {
 
-// Exposed publicly for tests.
-// TODO(miguelg) we can probably get rid of this now.
-extern const base::Feature kAllowFullscreenAppNotificationsFeature;
-
 // Handler for notifications shown by extensions. Will be created and owned by
 // the NativeNotificationDisplayService.
 class ExtensionNotificationHandler : public NotificationHandler {
  public:
   ExtensionNotificationHandler();
   ~ExtensionNotificationHandler() override;
 
   // NotificationHandler implementation.
   void OnShow(Profile* profile, const std::string& notification_id) override;
   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;
-  bool ShouldDisplayOnFullScreen(Profile* profile,
-                                 const std::string& origin) 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_