Use bytestringC rather than raw ptr/len pairs in syntax parser

core/fxcrt/include/fx_string.h

 // 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
 
 #ifndef CORE_FXCRT_INCLUDE_FX_STRING_H_
 #define CORE_FXCRT_INCLUDE_FX_STRING_H_
 
 #include <stdint.h>  // For intptr_t.
 #include <algorithm>
 
 #include "core/fxcrt/cfx_string_data_template.h"
 #include "core/fxcrt/include/cfx_retain_ptr.h"
 #include "core/fxcrt/include/fx_memory.h"
 #include "core/fxcrt/include/fx_system.h"
 
 class CFX_ByteString;
 class CFX_WideString;
 
 // An immutable string with caller-provided storage which must outlive the
-// string itself.
+// string itself. These are not necessarily nul-terminated, so that substring
+// extraction (via the Mid() method) is copy-free.
 class CFX_ByteStringC {
  public:
   typedef FX_CHAR value_type;
 
   CFX_ByteStringC() {
     m_Ptr = NULL;
     m_Length = 0;
   }
 
   CFX_ByteStringC(const uint8_t* ptr, FX_STRSIZE size) {
@@ skipping 634 matching lines @@
 }
 
 FX_FLOAT FX_atof(const CFX_ByteStringC& str);
 inline FX_FLOAT FX_atof(const CFX_WideStringC& wsStr) {
   return FX_atof(FX_UTF8Encode(wsStr.c_str(), wsStr.GetLength()).c_str());
 }
 void FX_atonum(const CFX_ByteStringC& str, FX_BOOL& bInteger, void* pData);
 FX_STRSIZE FX_ftoa(FX_FLOAT f, FX_CHAR* buf);
 
 #endif  // CORE_FXCRT_INCLUDE_FX_STRING_H_