Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

core/fpdfapi/fpdf_font/fpdf_font_cid.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/fpdfapi/fpdf_font/font_int.h"
 
 #include "core/fpdfapi/fpdf_cmaps/cmap_int.h"
 #include "core/fpdfapi/fpdf_font/ttgsubtable.h"
@@ skipping 422 matching lines @@
                                       ? CPDF_CMap::TwoBytes
                                       : CPDF_CMap::OneByte;
       }
       m_Status = 0;
     } else {
       if (word.GetLength() == 0 || word.GetAt(0) != '<') {
         return;
       }
       if (m_CodeSeq % 2) {
         CMap_CodeRange range;
-        if (CMap_GetCodeRange(range, m_LastWord, word)) {
+        if (CMap_GetCodeRange(range, m_LastWord.AsByteStringC(), word)) {
           m_CodeRanges.Add(range);
         }
       }
       m_CodeSeq++;
     }
   }
   m_LastWord = word;
 }
 
 // Static.
@@ skipping 334 matching lines @@
   FPDFAPI_LoadCID2UnicodeMap(charset, m_pEmbeddedMap, m_EmbeddedCount);
 }
 
 CIDSet CharsetFromOrdering(const CFX_ByteString& ordering) {
   for (size_t charset = 1; charset < FX_ArraySize(g_CharsetNames); ++charset) {
     if (ordering == CFX_ByteStringC(g_CharsetNames[charset]))
       return CIDSetFromSizeT(charset);
   }
   return CIDSET_UNKNOWN;
 }