[CleanUp] Remove parameter |by_user| in NotificationClosed

content/public/browser/desktop_notification_delegate.h

 // Copyright 2014 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 CONTENT_PUBLIC_BROWSER_DESKTOP_NOTIFICATION_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_DESKTOP_NOTIFICATION_DELEGATE_H_
 
 namespace content {
 
 // A delegate used by ContentBrowserClient::ShowDesktopNotification to report
 // the result of a desktop notification.
 class DesktopNotificationDelegate {
  public:
   virtual ~DesktopNotificationDelegate() {}
 
   // The notification was shown.
   virtual void NotificationDisplayed() = 0;
 
   // The notification was closed.
-  virtual void NotificationClosed(bool by_user) = 0;
+  virtual void NotificationClosed() = 0;
 
   // The user clicked on the notification.
   virtual void NotificationClick() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DESKTOP_NOTIFICATION_DELEGATE_H_