Move core/fpdfapi/fpdf_page to core/fpdfapi/page

core/fpdfapi/fpdf_page/cpdf_pageobjectlist.cpp

-// Copyright 2016 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/fpdfapi/fpdf_page/cpdf_pageobjectlist.h"
-
-#include "core/fpdfapi/fpdf_page/pageint.h"
-#include "third_party/base/stl_util.h"
-
-CPDF_PageObject* CPDF_PageObjectList::GetPageObjectByIndex(int index) {
-  if (index < 0 || index >= pdfium::CollectionSize<int>(*this))
-    return nullptr;
-  return (*this)[index].get();
-}