Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

core/fpdfdoc/cpvt_color.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_color.h"
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_simple_parser.h"
 
 // Static.
 CPVT_Color CPVT_Color::ParseColor(const CFX_ByteString& str) {
-  CPDF_SimpleParser syntax(str);
+  CPDF_SimpleParser syntax(str.AsByteStringC());
   if (syntax.FindTagParamFromStart("g", 1))
     return CPVT_Color(CPVT_Color::kGray, FX_atof(syntax.GetWord()));
 
   if (syntax.FindTagParamFromStart("rg", 3)) {
     FX_FLOAT f1 = FX_atof(syntax.GetWord());
     FX_FLOAT f2 = FX_atof(syntax.GetWord());
     FX_FLOAT f3 = FX_atof(syntax.GetWord());
     return CPVT_Color(CPVT_Color::kRGB, f1, f2, f3);
   }
   if (syntax.FindTagParamFromStart("k", 4)) {
@@ skipping 18 matching lines @@
                       array.GetFloatAt(1), array.GetFloatAt(2));
       break;
     case 4:
       rt = CPVT_Color(CPVT_Color::kCMYK, array.GetFloatAt(0),
                       array.GetFloatAt(1), array.GetFloatAt(2),
                       array.GetFloatAt(3));
       break;
   }
   return rt;
 }