Use virtual function to retrieve interface pointer

xfa/fwl/lightwidget/cfwl_listbox.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef XFA_FWL_LIGHTWIDGET_CFWL_LISTBOX_H_
 #define XFA_FWL_LIGHTWIDGET_CFWL_LISTBOX_H_
 
 #include <memory>
 #include <vector>
 
 #include "xfa/fwl/basewidget/ifwl_listbox.h"
 #include "xfa/fwl/core/fwl_error.h"
 #include "xfa/fwl/core/ifwl_widget.h"
 #include "xfa/fwl/lightwidget/cfwl_widget.h"
 
 class CFWL_ListItem;
 
 class CFWL_ListBox : public CFWL_Widget {
  public:
   CFWL_ListBox();
   ~CFWL_ListBox() override;
 
+  IFWL_ListBox* GetWidget() override;
+  const IFWL_ListBox* GetWidget() const override;
+
   static CFWL_ListBox* Create();
   FWL_Error Initialize(const CFWL_WidgetProperties* pProperties = nullptr);
   FWL_Error AddDIBitmap(CFX_DIBitmap* pDIB, IFWL_ListItem* pItem);
   IFWL_ListItem* AddString(const CFX_WideStringC& wsAdd,
                            FX_BOOL bSelect = FALSE);
   FX_BOOL DeleteString(IFWL_ListItem* pItem);
   void DeleteAll();
   int32_t CountSelItems();
   IFWL_ListItem* GetSelItem(int32_t nIndexSel);
   int32_t GetSelIndex(int32_t nIndex);
@@ skipping 77 matching lines @@
   CFX_RectF m_rtItem;
   uint32_t m_dwStates;
   CFX_WideString m_wsText;
   CFX_DIBitmap* m_pDIB;
   void* m_pData;
   uint32_t m_dwCheckState;
   CFX_RectF m_rtCheckBox;
 };
 
 #endif  // XFA_FWL_LIGHTWIDGET_CFWL_LISTBOX_H_