Remove DialogDelegate::OnClosed() which is redundant with

ui/views/window/dialog_delegate.h

 // Copyright (c) 2012 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 UI_VIEWS_WINDOW_DIALOG_DELEGATE_H_
 #define UI_VIEWS_WINDOW_DIALOG_DELEGATE_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
@@ skipping 91 matching lines @@
   DialogDelegate* AsDialogDelegate() override;
   ClientView* CreateClientView(Widget* widget) override;
   NonClientFrameView* CreateNonClientFrameView(Widget* widget) override;
 
   // Create a frame view using the new dialog style.
   static NonClientFrameView* CreateDialogFrameView(Widget* widget);
 
   // Returns whether this particular dialog should use the new dialog style.
   virtual bool UseNewStyleForThisDialog() const;
 
-  // Called when the window has been closed.
-  virtual void OnClosed() {}
-
   // A helper for accessing the DialogClientView object contained by this
   // delegate's Window.
   const DialogClientView* GetDialogClientView() const;
   DialogClientView* GetDialogClientView();
 
  protected:
   // Overridden from WidgetDelegate:
   ui::AXRole GetAccessibleWindowRole() const override;
 
  private:
@@ skipping 22 matching lines @@
   void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DialogDelegateView);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WINDOW_DIALOG_DELEGATE_H_