Split xfa_document_serialize into class files

xfa/fxfa/parser/cxfa_dataexporter.h

-// Copyright 2014 PDFium Authors. All rights reserved.
+// 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 XFA_FXFA_PARSER_XFA_DOCUMENT_SERIALIZE_H_
-#define XFA_FXFA_PARSER_XFA_DOCUMENT_SERIALIZE_H_
+#ifndef XFA_FXFA_PARSER_CXFA_DATAEXPORTER_H_
+#define XFA_FXFA_PARSER_CXFA_DATAEXPORTER_H_
 
 #include "core/fxcrt/include/fx_string.h"
 
 class CXFA_Document;
 class CXFA_Node;
-class IFX_FileRead;
 class IFX_FileWrite;
 class IFX_Stream;
 
-class CXFA_DataImporter {
- public:
-  explicit CXFA_DataImporter(CXFA_Document* pDocument);
-
-  FX_BOOL ImportData(IFX_FileRead* pDataDocument);
-
- protected:
-  CXFA_Document* const m_pDocument;
-};
-
 class CXFA_DataExporter {
  public:
   explicit CXFA_DataExporter(CXFA_Document* pDocument);
 
   FX_BOOL Export(IFX_FileWrite* pWrite);
   FX_BOOL Export(IFX_FileWrite* pWrite,
                  CXFA_Node* pNode,
-                 uint32_t dwFlag = 0,
-                 const FX_CHAR* pChecksum = nullptr);
+                 uint32_t dwFlag,
+                 const FX_CHAR* pChecksum);
 
  protected:
   FX_BOOL Export(IFX_Stream* pStream,
                  CXFA_Node* pNode,
                  uint32_t dwFlag,
                  const FX_CHAR* pChecksum);
 
   CXFA_Document* const m_pDocument;
 };
 
-#endif  // XFA_FXFA_PARSER_XFA_DOCUMENT_SERIALIZE_H_
+#endif  // XFA_FXFA_PARSER_CXFA_DATAEXPORTER_H_