Add NotificationAction.action member

public/platform/modules/notifications/WebNotificationAction.h

 // Copyright 2015 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 WebNotificationAction_h
 #define WebNotificationAction_h
 
 #include "public/platform/WebString.h"
 
 namespace blink {
 
 // Structure representing the data associated with a Web Notification action.
 struct WebNotificationAction {
     // Empty and copy constructor only for WebVector.
     WebNotificationAction() = default;
     WebNotificationAction(const WebNotificationAction&) = default;
 
-    WebNotificationAction(const WebString& title)
-        : title(title)
+    WebNotificationAction(const WebString& action, const WebString& title)
+        : action(action)
+        , title(title)
     {
     }
 
+    WebString action;
     WebString title;
 };
 
 } // namespace blink
 
 #endif // WebNotificationAction_h