Add a simple check for V4 cross reference table

core/fpdfapi/fpdf_parser/include/cpdf_parser.h

 // Copyright 2016 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 CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_PARSER_H_
 #define CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_PARSER_H_
 
 #include <map>
@@ skipping 96 matching lines @@
   Error SetEncryptHandler();
   void ReleaseEncryptHandler();
   FX_BOOL LoadLinearizedAllCrossRefV4(FX_FILESIZE pos, uint32_t dwObjCount);
   FX_BOOL LoadLinearizedCrossRefV4(FX_FILESIZE pos, uint32_t dwObjCount);
   FX_BOOL LoadLinearizedAllCrossRefV5(FX_FILESIZE pos);
   Error LoadLinearizedMainXRefTable();
   CPDF_StreamAcc* GetObjectStream(uint32_t number);
   FX_BOOL IsLinearizedFile(IFX_FileRead* pFileAccess, uint32_t offset);
   void SetEncryptDictionary(CPDF_Dictionary* pDict);
   void ShrinkObjectMap(uint32_t size);
+  // A simple check whether the cross reference table matches with
+  // the objects.
+  bool VerifyCrossRefV4();
 
   CPDF_Document* m_pDocument;
   std::unique_ptr<CPDF_SyntaxParser> m_pSyntax;
   bool m_bOwnFileRead;
   int m_FileVersion;
   CPDF_Dictionary* m_pTrailer;
   CPDF_Dictionary* m_pEncryptDict;
   FX_FILESIZE m_LastXRefOffset;
   FX_BOOL m_bXRefStream;
   std::unique_ptr<CPDF_SecurityHandler> m_pSecurityHandler;
@@ skipping 37 matching lines @@
     kPostObjNum,
     kGenNum,
     kPostGenNum,
     kTrailer,
     kBeginObj,
     kEndObj
   };
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_PARSER_H_