Fix ALL the include guards.

core/include/fpdfapi/fpdf_serial.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 _FPDF_SERIAL_
-#define _FPDF_SERIAL_
-#ifndef _FPDF_PAGE_
+#ifndef CORE_INCLUDE_FPDFAPI_FPDF_SERIAL_H_
+#define CORE_INCLUDE_FPDFAPI_FPDF_SERIAL_H_
+
 #include "fpdf_page.h"
-#endif
-#ifndef _FPDF_PAGEOBJ_H_
 #include "fpdf_pageobj.h"
-#endif
+
 class CPDF_ObjectStream;
 class CPDF_XRefStream;
 CFX_ByteTextBuf& operator << (CFX_ByteTextBuf& buf, const CPDF_Object* pObj);
 class CPDF_ObjArchiveSaver : public CFX_ArchiveSaver
 {
 public:
 
     friend CPDF_ObjArchiveSaver&        operator << (CPDF_ObjArchiveSaver& ar, const CPDF_Object* pObj);
 protected:
 
@@ skipping 170 matching lines @@
 
     CFX_DWordListArray          m_ObjectSize;
     CFX_DWordArray              m_NewObjNumArray;
 
     CPDF_Array*                 m_pIDArray;
 
     FX_INT32                    m_FileVersion;
     friend class CPDF_ObjectStream;
     friend class CPDF_XRefStream;
 };
-#endif
+
+#endif  // CORE_INCLUDE_FPDFAPI_FPDF_SERIAL_H_