Fix XFA compilation noise, part 1.

fpdfsdk/include/formfiller/FFL_ComboBox.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 FPDFSDK_INCLUDE_FORMFILLER_FFL_COMBOBOX_H_
 #define FPDFSDK_INCLUDE_FORMFILLER_FFL_COMBOBOX_H_
 
 #include "../../../core/include/fxcrt/fx_string.h"
@@ skipping 37 matching lines @@
   CPWL_Wnd* ResetPDFWindow(CPDFSDK_PageView* pPageView,
                            FX_BOOL bRestoreValue) override;
 
   // IPWL_FocusHandler:
   void OnSetFocus(CPWL_Wnd* pWnd) override;
   void OnKillFocus(CPWL_Wnd* pWnd) override;
 
   // IPWL_Edit_Notify:
   void OnAddUndo(CPWL_Edit* pEdit) override;
 
-  virtual FX_BOOL IsFieldFull(CPDFSDK_PageView* pPageView);
+  // CFFL_FormFiller:
+  FX_BOOL IsFieldFull(CPDFSDK_PageView* pPageView) override;
 
  private:
   CFX_WideString GetSelectExportText();
 
   CBA_FontMap* m_pFontMap;
   FFL_ComboBoxState m_State;
 };
 
 #endif  // FPDFSDK_INCLUDE_FORMFILLER_FFL_COMBOBOX_H_