Add CFX_ByteStringC::CharAt() to avoid c_str() and casts

core/fxcrt/fx_basic_bstring.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 <stddef.h>
 
 #include <algorithm>
 #include <cctype>
@@ skipping 81 matching lines @@
         StringData::Create(reinterpret_cast<const FX_CHAR*>(pStr), nLen));
   }
 }
 
 CFX_ByteString::CFX_ByteString(char ch) {
   m_pData.Reset(StringData::Create(1));
   m_pData->m_String[0] = ch;
 }
 
 CFX_ByteString::CFX_ByteString(const CFX_ByteStringC& stringSrc) {
-  if (!stringSrc.IsEmpty()) {
+  if (!stringSrc.IsEmpty())
     m_pData.Reset(StringData::Create(stringSrc.c_str(), stringSrc.GetLength()));
-  }
 }
 
 CFX_ByteString::CFX_ByteString(const CFX_ByteStringC& str1,
                                const CFX_ByteStringC& str2) {
   int nNewLen = str1.GetLength() + str2.GetLength();
   if (nNewLen == 0)
     return;
 
   m_pData.Reset(StringData::Create(nNewLen));
   m_pData->CopyContents(str1.c_str(), str1.GetLength());
@@ skipping 881 matching lines @@
     fraction %= scale;
     scale /= 10;
   }
   return buf_size;
 }
 CFX_ByteString CFX_ByteString::FormatFloat(FX_FLOAT d, int precision) {
   FX_CHAR buf[32];
   FX_STRSIZE len = FX_ftoa(d, buf);
   return CFX_ByteString(buf, len);
 }