Add ptr_util.h from base until std::make_unique<> available

xfa/fde/xml/cfx_saxreader.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 "xfa/fde/xml/cfx_saxreader.h"
 
 #include <algorithm>
 #include <utility>
 
+#include "third_party/base/ptr_util.h"
 #include "xfa/fxfa/xfa_checksum.h"
 
 enum class CFX_SaxMode {
   Text = 0,
   NodeStart,
   DeclOrComment,
   DeclNode,
   Comment,
   CommentContent,
   TagName,
@@ skipping 130 matching lines @@
   m_SkipChar = 0;
   m_iDataLength = 0;
   m_iEntityStart = -1;
   m_iNameLength = 0;
   m_iDataPos = 0;
   delete m_pCommentContext;
   m_pCommentContext = nullptr;
 }
 
 void CFX_SAXReader::Push() {
-  std::unique_ptr<CFX_SAXItem> pNew(WrapUnique(new CFX_SAXItem(++m_dwItemID)));
+  std::unique_ptr<CFX_SAXItem> pNew =
+      pdfium::MakeUnique<CFX_SAXItem>(++m_dwItemID);
   if (!m_Stack.empty())
     pNew->m_bSkip = m_Stack.top()->m_bSkip;
   m_Stack.push(std::move(pNew));
 }
 
 void CFX_SAXReader::Pop() {
   if (!m_Stack.empty())
     m_Stack.pop();
 }
 
@@ skipping 552 matching lines @@
   CFX_SAXItem* pItem = GetCurrentItem();
   if (!pItem)
     return;
 
   pItem->m_bSkip = TRUE;
 }
 
 void CFX_SAXReader::SetHandler(CXFA_SAXReaderHandler* pHandler) {
   m_pHandler = pHandler;
 }