Remove unused CFWL_ListBox code

xfa/fwl/cfwl_combobox.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/cfwl_combobox.h"
 
 #include <algorithm>
 #include <memory>
@@ skipping 32 matching lines @@
 
   if (m_pWidgetMgr->IsFormDisabled()) {
     DisForm_InitComboList();
     DisForm_InitComboEdit();
     return;
   }
 
   auto prop = pdfium::MakeUnique<CFWL_WidgetProperties>();
   prop->m_pThemeProvider = m_pProperties->m_pThemeProvider;
   prop->m_dwStyles |= FWL_WGTSTYLE_Border | FWL_WGTSTYLE_VScroll;
-  if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_CMB_ListItemIconText)
-    prop->m_dwStyleExes |= FWL_STYLEEXT_LTB_Icon;
   m_pListBox =
       pdfium::MakeUnique<CFWL_ComboList>(m_pOwnerApp, std::move(prop), this);
 
   if ((m_pProperties->m_dwStyleExes & FWL_STYLEEXT_CMB_DropDown) && !m_pEdit) {
     m_pEdit = pdfium::MakeUnique<CFWL_ComboEdit>(
         m_pOwnerApp, pdfium::MakeUnique<CFWL_WidgetProperties>(), this);
     m_pEdit->SetOuter(this);
   }
   if (m_pEdit)
     m_pEdit->SetParent(this);
@@ skipping 994 matching lines @@
       else
         iCurSel++;
     }
     m_iCurSel = iCurSel;
     SyncEditText(m_iCurSel);
     return;
   }
   if (m_pEdit)
     m_pEdit->GetDelegate()->OnProcessMessage(pMsg);
 }