Fix IWYU in formfiller/ directory.

fpdfsdk/include/formfiller/FFL_TextField.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
 
 #if !defined(AFX_FFL_EDIT_H__8E0C9456_CBA2_4EFB_9F31_53C6D8C1A8AC__INCLUDED_)
 #define AFX_FFL_EDIT_H__8E0C9456_CBA2_4EFB_9F31_53C6D8C1A8AC__INCLUDED_
 
 #include "FFL_FormFiller.h"
 
 #define BF_ALIGN_LEFT                   0
 #define BF_ALIGN_MIDDLE                 1
 #define BF_ALIGN_RIGHT                  2
 
 class CBA_FontMap;
 
-class CFFL_EditUndoItem //: public IUndoItem
+
+class CFFL_EditUndoItem
 {
 public:
         CFFL_EditUndoItem(CPWL_Edit* pEdit);
         virtual ~CFFL_EditUndoItem();
         
         virtual void                                    Undo();
         virtual void                                    Redo();
         virtual CFX_WideString                  GetDescr();
         virtual void                                    Release();
 };
@@ skipping 48 matching lines @@
         virtual void                            DoPaste(CPDFSDK_Document* pDocument); 
         
 private:
         CBA_FontMap*                            m_pFontMap;
 //      CBA_SpellCheck*                         m_pSpellCheck;
         FFL_TextFieldState                      m_State;
 //      CFFL_IM_BOX                                     m_IMBox;
 };
 
 #endif // !defined(AFX_FFL_EDIT_H__8E0C9456_CBA2_4EFB_9F31_53C6D8C1A8AC__INCLUDED_)