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

core/src/fpdfdoc/doc_viewerPreferences.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/fpdfdoc/fpdf_doc.h"
 
 CPDF_ViewerPreferences::CPDF_ViewerPreferences(CPDF_Document* pDoc)
     : m_pDoc(pDoc) {}
 CPDF_ViewerPreferences::~CPDF_ViewerPreferences() {}
 FX_BOOL CPDF_ViewerPreferences::IsDirectionR2L() const {
   CPDF_Dictionary* pDict = m_pDoc->GetRoot();
   pDict = pDict->GetDictBy("ViewerPreferences");
   if (!pDict) {
     return FALSE;
@@ skipping 27 matching lines @@
   return pRange;
 }
 CFX_ByteString CPDF_ViewerPreferences::Duplex() const {
   CPDF_Dictionary* pDict = m_pDoc->GetRoot();
   pDict = pDict->GetDictBy("ViewerPreferences");
   if (!pDict) {
     return "None";
   }
   return pDict->GetStringBy("Duplex");
 }