Fix missing or broken include guard macros in pdfium headers.

core/src/fpdfapi/fpdf_page/pageint.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 _PAGEINT_H_
+#define _PAGEINT_H_
+
 #include "../../../include/fpdfapi/fpdf_pageobj.h"
 #define PARSE_STEP_LIMIT                100
 #define STREAM_PARSE_BUFSIZE    20480
 class CPDF_QuickFontCache;
 #ifndef _FPDFAPI_MINI_
 class CPDF_StreamParser : public CFX_Object
 {
 public:
 
     CPDF_StreamParser(const FX_BYTE* pData, FX_DWORD dwSize);
@@ skipping 479 matching lines @@
 public:
     struct _NamingState : public CFX_Object {
         CFX_ByteString  m_Prefix;
         int                             m_nIndex;
     };
     ~CPDF_ResourceNaming();
     CFX_ByteString              GetName(const CPDF_Dictionary* pResList, FX_LPCSTR szType);
 protected:
     CFX_MapByteStringToPtr      m_NamingCache;
 };
+
+#endif  // _PAGEINT_H_