IFWL cleanup in the Combo classes

xfa/fwl/core/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_CORE_CFWL_LISTBOX_H_
 #define XFA_FWL_CORE_CFWL_LISTBOX_H_
 
 #include <memory>
 #include <vector>
 
 #include "xfa/fwl/core/cfwl_widget.h"
 #include "xfa/fwl/core/fwl_error.h"
 #include "xfa/fwl/core/ifwl_listbox.h"
 #include "xfa/fwl/core/ifwl_widget.h"
 
 class CFWL_ListBox : public CFWL_Widget, public IFWL_ListBoxDP {
  public:
   CFWL_ListBox(const IFWL_App*);
   ~CFWL_ListBox() override;
 
   void Initialize();
 
   // IFWL_DataProvider:
   void GetCaption(IFWL_Widget* pWidget, CFX_WideString& wsCaption) override;
 
   // IFWL_ListBoxDP:
-  int32_t CountItems(const IFWL_Widget* pWidget) override;
-  CFWL_ListItem* GetItem(const IFWL_Widget* pWidget, int32_t nIndex) override;
+  int32_t CountItems(const IFWL_Widget* pWidget) const override;
+  CFWL_ListItem* GetItem(const IFWL_Widget* pWidget,
+                         int32_t nIndex) const override;
   int32_t GetItemIndex(IFWL_Widget* pWidget, CFWL_ListItem* pItem) override;
   bool SetItemIndex(IFWL_Widget* pWidget,
                     CFWL_ListItem* pItem,
                     int32_t nIndex) override;
   uint32_t GetItemStyles(IFWL_Widget* pWidget, CFWL_ListItem* pItem) override;
   void GetItemText(IFWL_Widget* pWidget,
                    CFWL_ListItem* pItem,
                    CFX_WideString& wsText) override;
   void GetItemRect(IFWL_Widget* pWidget,
                    CFWL_ListItem* pItem,
@@ skipping 33 matching lines @@
   CFWL_ListItem* GetSelItem(int32_t nIndexSel);
   int32_t GetSelIndex(int32_t nIndex);
 
   void GetScrollPos(FX_FLOAT& fPos, bool bVert = true);
 
   CFWL_ListItem* GetItem(int32_t nIndex);
   void GetItemText(CFWL_ListItem* pItem, CFX_WideString& wsText);
   uint32_t GetItemStates(CFWL_ListItem* pItem);
 
  private:
-  int32_t CountItems();
+  int32_t CountItems() const;
 
   std::vector<std::unique_ptr<CFWL_ListItem>> m_ItemArray;
 };
 
 #endif  // XFA_FWL_CORE_CFWL_LISTBOX_H_