Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

core/fpdfapi/fpdf_parser/cpdf_parser.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_parser/include/cpdf_parser.h"
 
 #include <vector>
 
@@ skipping 804 matching lines @@
                           (pRef && IsValidObjectNumber(pRef->GetRefObjNum()) &&
                            m_ObjectInfo[pRef->GetRefObjNum()].pos != 0)) {
                         auto it = pTrailer->begin();
                         while (it != pTrailer->end()) {
                           const CFX_ByteString& key = it->first;
                           CPDF_Object* pElement = it->second;
                           ++it;
                           uint32_t dwObjNum =
                               pElement ? pElement->GetObjNum() : 0;
                           if (dwObjNum) {
-                            m_pTrailer->SetAtReference(key, m_pDocument,
-                                                       dwObjNum);
+                            m_pTrailer->SetAtReference(key.AsByteStringC(),
+                                                       m_pDocument, dwObjNum);
                           } else {
-                            m_pTrailer->SetAt(key, pElement->Clone());
+                            m_pTrailer->SetAt(key.AsByteStringC(),
+                                              pElement->Clone());
                           }
                         }
                       }
                       pObj->Release();
                     } else {
                       if (pObj->IsStream()) {
                         m_pTrailer = ToDictionary(pTrailer->Clone());
                         pObj->Release();
                       } else {
                         m_pTrailer = pTrailer;
@@ skipping 804 matching lines @@
   if (!LoadLinearizedAllCrossRefV4(m_LastXRefOffset, m_dwXrefStartObjNum) &&
       !LoadLinearizedAllCrossRefV5(m_LastXRefOffset)) {
     m_LastXRefOffset = 0;
     m_pSyntax->m_MetadataObjnum = dwSaveMetadataObjnum;
     return FORMAT_ERROR;
   }
 
   m_pSyntax->m_MetadataObjnum = dwSaveMetadataObjnum;
   return SUCCESS;
 }