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

core/src/fpdfdoc/doc_formcontrol.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 <algorithm>
 
+#include "core/include/fpdfapi/cpdf_document.h"
 #include "core/include/fpdfdoc/fpdf_doc.h"
 
 CPDF_FormControl::CPDF_FormControl(CPDF_FormField* pField,
                                    CPDF_Dictionary* pWidgetDict) {
   m_pField = pField;
   m_pWidgetDict = pWidgetDict;
   m_pForm = m_pField->m_pForm;
 }
 CFX_FloatRect CPDF_FormControl::GetRect() const {
   return m_pWidgetDict->GetRectBy("Rect");
@@ skipping 402 matching lines @@
 }
 
 CPDF_IconFit CPDF_ApSettings::GetIconFit() const {
   return CPDF_IconFit(m_pDict ? m_pDict->GetDictBy("IF") : nullptr);
 }
 
 int CPDF_ApSettings::GetTextPosition() const {
   return m_pDict ? m_pDict->GetIntegerBy("TP", TEXTPOS_CAPTION)
                  : TEXTPOS_CAPTION;
 }