Show only one instance of the keyboard overlay.

chrome/browser/ui/views/keyboard_overlay_dialog_view.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 CHROME_BROWSER_UI_VIEWS_KEYBOARD_OVERLAY_DIALOG_VIEW_H_
 #define CHROME_BROWSER_UI_VIEWS_KEYBOARD_OVERLAY_DIALOG_VIEW_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "chrome/browser/ui/views/web_dialog_view.h"
 
 class Profile;
 
 namespace ui {
 class WebDialogDelegate;
 }
 
 // A customized dialog view for the keyboard overlay.
 class KeyboardOverlayDialogView : public WebDialogView {
  public:
   KeyboardOverlayDialogView(Profile* profile, ui::WebDialogDelegate* delegate);
   virtual ~KeyboardOverlayDialogView();
 
   // Shows the keyboard overlay.
   static void ShowDialog();
 
+ private:
+  // Overridden from views::WidgetDelegate:
+  virtual void WindowClosing() OVERRIDE;
+
   DISALLOW_COPY_AND_ASSIGN(KeyboardOverlayDialogView);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_KEYBOARD_OVERLAY_DIALOG_VIEW_H_