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

core/src/fpdfapi/fpdf_page/fpdf_page_image.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_page/pageint.h"
 
+#include "core/include/fpdfapi/cpdf_document.h"
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fpdfapi/fpdf_pageobj.h"
 
 CPDF_ImageObject::CPDF_ImageObject() : m_pImage(nullptr) {}
 
 CPDF_ImageObject::~CPDF_ImageObject() {
   if (!m_pImage) {
     return;
   }
   if (m_pImage->IsInline() ||
@@ skipping 70 matching lines @@
     m_pInlineDict = ToDictionary(pDict->Clone());
   }
   m_pOC = pDict->GetDictBy("OC");
   m_bIsMask =
       !pDict->KeyExist("ColorSpace") || pDict->GetIntegerBy("ImageMask");
   m_bInterpolate = pDict->GetIntegerBy("Interpolate");
   m_Height = pDict->GetIntegerBy("Height");
   m_Width = pDict->GetIntegerBy("Width");
   return TRUE;
 }