Fix probably harmless thinko in StringCharAt (causes...

src/string.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 44 matching lines @@
 // ECMA-262 section 15.5.4.3
 function StringValueOf() {
   if (!IS_STRING(this) && !%HasStringClass(this))
     throw new $TypeError('String.prototype.valueOf is not generic');
   return %_ValueOf(this);
 }
 
 
 // ECMA-262, section 15.5.4.4
 function StringCharAt(pos) {
-  var char_code = %_FastCharCodeAt(subject, index);
+  var char_code = %_FastCharCodeAt(this, index);
   if (!%_IsSmi(char_code)) {
     var subject = ToString(this);
     var index = TO_INTEGER(pos);
     if (index >= subject.length || index < 0) return "";
     char_code = %StringCharCodeAt(subject, index);
   }
   return %CharFromCode(char_code);
 }
 
 
@@ skipping 807 matching lines @@
     "italics", StringItalics,
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
     "sup", StringSup
   ));
 }
 
 
 SetupString();