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

core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.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/src/fpdfapi/fpdf_render/render_int.h"
 
 #include <algorithm>
 #include <memory>
 #include <vector>
 
+#include "core/include/fpdfapi/cpdf_document.h"
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_pageobj.h"
 #include "core/include/fpdfapi/fpdf_render.h"
 #include "core/include/fxcodec/fx_codec.h"
 #include "core/include/fxcrt/fx_safe_types.h"
 #include "core/include/fxge/fx_ge.h"
 #include "core/src/fpdfapi/fpdf_page/pageint.h"
 
 namespace {
 
@@ skipping 1618 matching lines @@
                                    IFX_Pause* pPause) {
   return LoadHandle->Continue(pPause);
 }
 
 CPDF_ImageLoader::~CPDF_ImageLoader() {
   if (!m_bCached) {
     delete m_pBitmap;
     delete m_pMask;
   }
 }