Remove the GetCaption dataprovider method

xfa/fwl/core/cfwl_listbox.cpp

 // 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
 
 #include "xfa/fwl/core/cfwl_listbox.h"
 
 #include <memory>
 #include <utility>
@@ skipping 81 matching lines @@
     return nullptr;
   return m_ItemArray[nIndex].get();
 }
 
 uint32_t CFWL_ListBox::GetItemStates(CFWL_ListItem* pItem) {
   if (!pItem)
     return 0;
   return pItem->m_dwStates | pItem->m_dwCheckState;
 }
 
-void CFWL_ListBox::GetCaption(IFWL_Widget* pWidget, CFX_WideString& wsCaption) {
-  wsCaption = L"";
-}
-
 int32_t CFWL_ListBox::CountItems(const IFWL_Widget* pWidget) const {
   return pdfium::CollectionSize<int32_t>(m_ItemArray);
 }
 
 CFWL_ListItem* CFWL_ListBox::GetItem(const IFWL_Widget* pWidget,
                                      int32_t nIndex) const {
   if (nIndex < 0 || nIndex >= CountItems(pWidget))
     return nullptr;
   return m_ItemArray[nIndex].get();
 }
@@ skipping 64 matching lines @@
 uint32_t CFWL_ListBox::GetItemCheckState(IFWL_Widget* pWidget,
                                          CFWL_ListItem* pItem) {
   return static_cast<CFWL_ListItem*>(pItem)->m_dwCheckState;
 }
 
 void CFWL_ListBox::SetItemCheckState(IFWL_Widget* pWidget,
                                      CFWL_ListItem* pItem,
                                      uint32_t dwCheckState) {
   static_cast<CFWL_ListItem*>(pItem)->m_dwCheckState = dwCheckState;
 }