Factor out uses of the WebContentsModalDialog interface from platform-independent code

chrome/browser/ui/tab_modal_confirm_dialog.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_TAB_MODAL_CONFIRM_DIALOG_H_
 #define CHROME_BROWSER_UI_TAB_MODAL_CONFIRM_DIALOG_H_
 
-class TabModalConfirmDialogDelegate;
+#include "chrome/browser/ui/tab_modal_confirm_dialog_delegate.h"
 
 namespace content {
 class WebContents;
 }
 
 // Base class for the tab modal confirm dialog.
-class TabModalConfirmDialog {
+class TabModalConfirmDialog : public TabModalConfirmDialogCloseDelegate {
  public:
   // Platform specific factory function. This function will automatically show
   // the dialog.
   static TabModalConfirmDialog* Create(TabModalConfirmDialogDelegate* delegate,
                                        content::WebContents* web_contents);
   // Accepts the dialog.
   virtual void AcceptTabModalDialog() = 0;
 
   // Cancels the dialog.
   virtual void CancelTabModalDialog() = 0;
 
+  // TabModalConfirmDialogCloseDelegate:
+  // Closes the dialog.
+  virtual void CloseDialog() = 0;
+
  protected:
   virtual ~TabModalConfirmDialog() {}
 };
 
 #endif  // CHROME_BROWSER_UI_TAB_MODAL_CONFIRM_DIALOG_H_