XFA: add CPDFDocumentToFPDFDocument()

fpdfsdk/src/fpdf_dataavail.cpp

 // 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
 
 #include "../../public/fpdf_dataavail.h"
 #include "../../public/fpdf_formfill.h"
 #include "../include/fsdk_define.h"
 #include "../include/fpdfxfa/fpdfxfa_doc.h"
@@ skipping 95 matching lines @@
 
   FX_DWORD err_code = pParser->StartAsynParse(
       ((CFPDF_DataAvail*)avail)->m_pDataAvail->GetFileRead());
   if (err_code) {
     delete pParser;
     ProcessParseError(err_code);
     return NULL;
   }
   ((CFPDF_DataAvail*)avail)->m_pDataAvail->SetDocument(pParser->GetDocument());
   CheckUnSupportError(pParser->GetDocument(), FPDF_ERR_SUCCESS);
-  CPDF_Document* pPDFDoc = pParser->GetDocument();
-  CPDFXFA_App* pApp = CPDFXFA_App::GetInstance();
-  return new CPDFXFA_Document(pPDFDoc, pApp);
+  return FPDFDocumentFromCPDFDocument(pParser->GetDocument());
 }
 
 DLLEXPORT int STDCALL FPDFAvail_GetFirstPageNum(FPDF_DOCUMENT doc) {
   CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(doc);
   return pDoc ? pDoc->GetParser()->GetFirstPageNo() : 0;
 }
 
 DLLEXPORT int STDCALL FPDFAvail_IsPageAvail(FPDF_AVAIL avail,
                                             int page_index,
                                             FX_DOWNLOADHINTS* hints) {
@@ skipping 10 matching lines @@
     return -1;
   CFPDF_DownloadHintsWrap hints_wrap(hints);
   return ((CFPDF_DataAvail*)avail)->m_pDataAvail->IsFormAvail(&hints_wrap);
 }
 
 DLLEXPORT FPDF_BOOL STDCALL FPDFAvail_IsLinearized(FPDF_AVAIL avail) {
   if (avail == NULL)
     return -1;
   return ((CFPDF_DataAvail*)avail)->m_pDataAvail->IsLinearizedPDF();
 }