Split off CPDF_Document into its own .cpp/.h files.

fpdfsdk/src/fpdfppo.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_ppo.h"
 
 #include <memory>
 
+#include "core/include/fpdfapi/cpdf_document.h"
 #include "fpdfsdk/include/fsdk_define.h"
 #include "third_party/base/stl_util.h"
 
 class CPDF_PageOrganizer {
  public:
   using ObjectNumberMap = std::map<FX_DWORD, FX_DWORD>;
   CPDF_PageOrganizer();
   ~CPDF_PageOrganizer();
 
   FX_BOOL PDFDocInit(CPDF_Document* pDestPDFDoc, CPDF_Document* pSrcPDFDoc);
@@ skipping 377 matching lines @@
   if (!pSrcDict)
     return FALSE;
 
   CPDF_Dictionary* pDstDict = pDstDoc->GetRoot();
   if (!pDstDict)
     return FALSE;
 
   pDstDict->SetAt("ViewerPreferences", pSrcDict->Clone(TRUE));
   return TRUE;
 }