Revert of Deprecate native and extension notification delegates.

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

 // Copyright (c) 2012 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_NOTIFICATIONS_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_NOTIFICATIONS_NOTIFICATIONS_API_H_
 
 #include <string>
 
 #include "base/feature_list.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/common/extensions/api/notifications.h"
 #include "extensions/browser/extension_function.h"
 #include "ui/message_center/notification_types.h"
 
 class Notification;
 
 namespace extensions {
 
+extern const base::Feature kAllowFullscreenAppNotificationsFeature;
+
 class ExtensionNotificationDisplayHelper;
 
 class NotificationsApiFunction : public ChromeAsyncExtensionFunction {
  public:
   // Whether the current extension and channel allow the API. Public for
   // testing.
   bool IsNotificationsApiAvailable();
 
  protected:
   NotificationsApiFunction();
@@ skipping 102 matching lines @@
   ~NotificationsGetPermissionLevelFunction() override;
 
  private:
   DECLARE_EXTENSION_FUNCTION("notifications.getPermissionLevel",
                              NOTIFICATIONS_GET_ALL)
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_NOTIFICATIONS_NOTIFICATIONS_API_H_