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

core/src/fpdfapi/fpdf_edit/fpdf_edit_content.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 "core/include/fpdfapi/cpdf_document.h"
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fpdfapi/fpdf_serial.h"
 #include "core/src/fpdfapi/fpdf_page/pageint.h"
 
 CFX_ByteTextBuf& operator<<(CFX_ByteTextBuf& ar, CFX_Matrix& matrix) {
   ar << matrix.a << " " << matrix.b << " " << matrix.c << " " << matrix.d << " "
      << matrix.e << " " << matrix.f;
   return ar;
 }
@@ skipping 132 matching lines @@
     CPDF_StreamAcc contentStream;
     contentStream.LoadAllData(pStream);
     ProcessForm(buf, contentStream.GetData(), contentStream.GetSize(), matrix);
   }
   CPDF_Stream* pStream = new CPDF_Stream(NULL, 0, NULL);
   pStream->SetData(buf.GetBuffer(), buf.GetLength(), FALSE, FALSE);
   m_pDocument->AddIndirectObject(pStream);
   m_pPage->m_pFormDict->SetAtReference("Contents", m_pDocument,
                                        pStream->GetObjNum());
 }