Replace a few more std::unique_ptr.reset() with WrapUnique assignments.

core/fxcrt/fx_xml_parser.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/fxcrt/xml_int.h"
 
 #include <vector>
 
@@ skipping 876 matching lines @@
     if (item.Matches(space, name))
       return &item.m_Value;
   }
   return nullptr;
 }
 
 void CXML_AttrMap::SetAt(const CFX_ByteString& space,
                          const CFX_ByteString& name,
                          const CFX_WideString& value) {
   if (!m_pMap)
-    m_pMap.reset(new std::vector<CXML_AttrItem>);
+    m_pMap = WrapUnique(new std::vector<CXML_AttrItem>);
 
   for (CXML_AttrItem& item : *m_pMap) {
     if (item.Matches(space, name)) {
       item.m_Value = value;
       return;
     }
   }
 
   m_pMap->push_back({space, name, CFX_WideString(value)});
 }
 
 int CXML_AttrMap::GetSize() const {
   return m_pMap ? pdfium::CollectionSize<int>(*m_pMap) : 0;
 }
 
 CXML_AttrItem& CXML_AttrMap::GetAt(int index) const {
   return (*m_pMap)[index];
 }