Remove DialogDelegate::OnClosed() which is redundant with

ash/system/chromeos/session/logout_confirmation_dialog.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 ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_CONFIRMATION_DIALOG_H_
 #define ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_CONFIRMATION_DIALOG_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/time/time.h"
@@ skipping 17 matching lines @@
                            base::TimeTicks logout_time);
   ~LogoutConfirmationDialog() override;
 
   void Update(base::TimeTicks logout_time);
 
   // views::DialogDelegateView:
   bool Accept() override;
   ui::ModalType GetModalType() const override;
   base::string16 GetWindowTitle() const override;
   base::string16 GetDialogButtonLabel(ui::DialogButton button) const override;
-  void OnClosed() override;
-  void DeleteDelegate() override;
+  void WindowClosing() override;
 
  private:
   void UpdateLabel();
 
   LogoutConfirmationController* controller_;
   base::TimeTicks logout_time_;
 
   views::Label* label_;
 
   base::RepeatingTimer update_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LogoutConfirmationDialog);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_CONFIRMATION_DIALOG_H_