Implement the Notification `timestamp` property

third_party/WebKit/Source/modules/notifications/Notification.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef Notification_h
 #define Notification_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/SerializedScriptValue.h"
 #include "core/dom/ActiveDOMObject.h"
+#include "core/dom/DOMTimeStamp.h"
 #include "modules/EventTargetModules.h"
 #include "modules/ModulesExport.h"
 #include "modules/vibration/NavigatorVibration.h"
 #include "platform/AsyncMethodRunner.h"
 #include "platform/heap/Handle.h"
 #include "platform/weborigin/KURL.h"
 #include "public/platform/WebVector.h"
 #include "public/platform/modules/notifications/WebNotificationData.h"
 #include "public/platform/modules/notifications/WebNotificationDelegate.h"
 #include "public/platform/modules/notifications/WebNotificationPermission.h"
@@ skipping 35 matching lines @@
     void dispatchErrorEvent() override;
     void dispatchCloseEvent() override;
 
     String title() const;
     String dir() const;
     String lang() const;
     String body() const;
     String tag() const;
     String icon() const;
     NavigatorVibration::VibrationPattern vibrate(bool& isNull) const;
+    DOMTimeStamp timestamp() const;
     bool silent() const;
     bool requireInteraction() const;
     ScriptValue data(ScriptState*);
     HeapVector<NotificationAction> actions() const;
 
     static String permissionString(WebNotificationPermission);
     static String permission(ExecutionContext*);
     static WebNotificationPermission checkPermission(ExecutionContext*);
     static ScriptPromise requestPermission(ScriptState*, NotificationPermissionCallback*);
 
@@ skipping 49 matching lines @@
     void setState(NotificationState state) { m_state = state; }
 
     NotificationState m_state;
 
     Member<AsyncMethodRunner<Notification>> m_asyncRunner;
 };
 
 } // namespace blink
 
 #endif // Notification_h