Cleanup forward declarations.

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 CORE_INCLUDE_FPDFAPI_FPDF_SERIAL_H_
 #define CORE_INCLUDE_FPDFAPI_FPDF_SERIAL_H_
 
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fpdfapi/fpdf_pageobj.h"
 
-class CPDF_ObjectStream;
 class CPDF_XRefStream;
 
 CFX_ByteTextBuf& operator<<(CFX_ByteTextBuf& buf, const CPDF_Object* pObj);
 
 #define FPDFCREATE_INCREMENTAL 1
 #define FPDFCREATE_NO_ORIGINAL 2
 #define FPDFCREATE_PROGRESSIVE 4
 #define FPDFCREATE_OBJECTSTREAM 8
 
 class CPDF_Creator {
@@ skipping 72 matching lines @@
   CFX_FileSizeListArray m_ObjectOffset;
   CFX_DWordArray m_NewObjNumArray;
   CPDF_Array* m_pIDArray;
   int32_t m_FileVersion;
 
   friend class CPDF_ObjectStream;
   friend class CPDF_XRefStream;
 };
 
 #endif  // CORE_INCLUDE_FPDFAPI_FPDF_SERIAL_H_