Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

core/fpdfdoc/cpvt_fontmap.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/fpdfdoc/cpvt_fontmap.h"
 
 #include "core/fpdfapi/fpdf_font/include/cpdf_font.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
@@ skipping 20 matching lines @@
   if (!pDoc || !pResDict)
     return;
 
   CFX_ByteString sFontAlias;
   CPDF_Dictionary* pFormDict = pDoc->GetRoot()->GetDictBy("AcroForm");
   CPDF_Font* pPDFFont = AddNativeInterFormFont(pFormDict, pDoc, sSysFontAlias);
   if (!pPDFFont)
     return;
 
   if (CPDF_Dictionary* pFontList = pResDict->GetDictBy("Font")) {
-    if (!pFontList->KeyExist(sSysFontAlias))
-      pFontList->SetAtReference(sSysFontAlias, pDoc, pPDFFont->GetFontDict());
+    if (!pFontList->KeyExist(sSysFontAlias.AsByteStringC()))
+      pFontList->SetAtReference(sSysFontAlias.AsByteStringC(), pDoc,
+                                pPDFFont->GetFontDict());
   }
   pSysFont = pPDFFont;
 }
 
 CPDF_Font* CPVT_FontMap::GetPDFFont(int32_t nFontIndex) {
   switch (nFontIndex) {
     case 0:
       return m_pDefFont;
     case 1:
       if (!m_pSysFont) {
@@ skipping 13 matching lines @@
     case 1:
       if (!m_pSysFont) {
         GetAnnotSysPDFFont(m_pDocument, m_pResDict, m_pSysFont,
                            m_sSysFontAlias);
       }
       return m_sSysFontAlias;
     default:
       return "";
   }
 }