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

chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.h

 // Copyright (c) 2011 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_COCOA_TAB_MODAL_CONFIRM_DIALOG_MAC_H_
 #define CHROME_BROWSER_UI_COCOA_TAB_MODAL_CONFIRM_DIALOG_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 20 matching lines @@
   TabModalConfirmDialogMac(TabModalConfirmDialogDelegate* delegate,
                            content::WebContents* web_contents);
 
  private:
   virtual ~TabModalConfirmDialogMac();
 
   // TabModalConfirmDialog:
   virtual void AcceptTabModalDialog() OVERRIDE;
   virtual void CancelTabModalDialog() OVERRIDE;
 
+  // TabModalConfirmDialogCloseDelegate:
+  virtual void CloseDialog() OVERRIDE;
+
   // ConstrainedWindowMacDelegate:
   virtual void OnConstrainedWindowClosed(
       ConstrainedWindowMac* window) OVERRIDE;
 
   scoped_ptr<ConstrainedWindowMac> window_;
   scoped_ptr<TabModalConfirmDialogDelegate> delegate_;
   scoped_nsobject<ConstrainedWindowAlert> alert_;
   scoped_nsobject<TabModalConfirmDialogMacBridge> bridge_;
 
   DISALLOW_COPY_AND_ASSIGN(TabModalConfirmDialogMac);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_TAB_MODAL_CONFIRM_DIALOG_MAC_H_