Add support for native extension notifications

chrome/browser/ui/cocoa/notifications/notification_constants_mac.mm

 // 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/ui/cocoa/notifications/notification_constants_mac.h"
 
 namespace notification_constants {
 
 // Applicable to NotificationBuilder and NotificationResponseBuilder
 NSString* const kNotificationOrigin = @"notificationOrigin";
 NSString* const kNotificationId = @"notificationId";
 NSString* const kNotificationProfileId = @"notificationProfileId";
 NSString* const kNotificationIncognito = @"notificationIncognito";
 NSString* const kNotificationType = @"notificationType";
+NSString* const kNotificationHasSettingsButton =
+    @"notificationHasSettingsButton";
 
 // Only applicable to the NotificationResponseBuilder
 NSString* const kNotificationOperation = @"notificationOperation";
 NSString* const kNotificationButtonIndex = @"notificationButtonIndex";
 
 // Name of the XPC service
 NSString* const kAlertXPCServiceName = @"%@.AlertNotificationService";
 
 }  // notification_constants