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

fpdfsdk/src/fpdf_transformpage.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_transformpage.h"
 
+#include "core/include/fpdfapi/cpdf_document.h"
 #include "fpdfsdk/include/fsdk_define.h"
 
 namespace {
 
 void SetBoundingBox(CPDF_Page* page,
                     const CFX_ByteStringC& key,
                     float left,
                     float bottom,
                     float right,
                     float top) {
@@ skipping 295 matching lines @@
       } else if (pDirectObj->IsStream()) {
         pContentArray = new CPDF_Array();
         pContentArray->AddReference(pDoc, pStream->GetObjNum());
         pContentArray->AddReference(pDoc, pDirectObj->GetObjNum());
         pPageDic->SetAtReference("Contents", pDoc,
                                  pDoc->AddIndirectObject(pContentArray));
       }
     }
   }
 }