This adds new methods to String object:

src/messages.js

 // Copyright 2012 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 108 matching lines @@
                                  ["Source is too large"],
   typed_array_set_negative_offset:
                                  ["Start offset is negative"],
   invalid_data_view_offset:      ["Start offset is outside the bounds of the buffer"],
   invalid_data_view_length:      ["Invalid data view length"],
   invalid_data_view_accessor_offset:
                                  ["Offset is outside the bounds of the DataView"],
 
   stack_overflow:                ["Maximum call stack size exceeded"],
   invalid_time_value:            ["Invalid time value"],
+  invalid_count_value:           ["Invalid count value"],
   // SyntaxError
   paren_in_arg_string:           ["Function arg string contains parenthesis"],
   not_isvar:                     ["builtin %IS_VAR: not a variable"],
   single_function_literal:       ["Single function literal required"],
   invalid_regexp_flags:          ["Invalid flags supplied to RegExp constructor '", "%0", "'"],
   invalid_regexp:                ["Invalid RegExp pattern /", "%0", "/"],
   illegal_break:                 ["Illegal break statement"],
   illegal_continue:              ["Illegal continue statement"],
   illegal_return:                ["Illegal return statement"],
   illegal_let:                   ["Illegal let declaration outside extended mode"],
@@ skipping 1197 matching lines @@
     %GetAndClearOverflowedStackTrace(this);
   };
 
   %DefineOrRedefineAccessorProperty(
       boilerplate, 'stack', getter, setter, DONT_ENUM);
 
   return boilerplate;
 }
 
 var kStackOverflowBoilerplate = SetUpStackOverflowBoilerplate();