Revert of [intrinsic] Drop the %_ValueOf intrinsic.

src/js/string.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
@@ skipping 19 matching lines @@
   IsRegExp = from.IsRegExp;
   MakeRangeError = from.MakeRangeError;
   MakeTypeError = from.MakeTypeError;
   MaxSimple = from.MaxSimple;
   MinSimple = from.MinSimple;
   RegExpInitialize = from.RegExpInitialize;
 });
 
 //-------------------------------------------------------------------
 
+// ECMA-262 section 15.5.4.2
+function StringToString() {
+  if (!IS_STRING(this) && !IS_STRING_WRAPPER(this)) {
+    throw MakeTypeError(kNotGeneric, 'String.prototype.toString');
+  }
+  return %_ValueOf(this);
+}
+
+
+// ECMA-262 section 15.5.4.3
+function StringValueOf() {
+  if (!IS_STRING(this) && !IS_STRING_WRAPPER(this)) {
+    throw MakeTypeError(kNotGeneric, 'String.prototype.valueOf');
+  }
+  return %_ValueOf(this);
+}
+
+
 // ECMA-262, section 15.5.4.6
 function StringConcat(other /* and more */) {  // length == 1
   "use strict";
   CHECK_OBJECT_COERCIBLE(this, "String.prototype.concat");
   var s = TO_STRING(this);
   var len = arguments.length;
   for (var i = 0; i < len; ++i) {
     s = s + TO_STRING(arguments[i]);
   }
   return s;
@@ skipping 681 matching lines @@
 
 // -------------------------------------------------------------------
 
 // Set up the non-enumerable functions on the String object.
 utils.InstallFunctions(GlobalString, DONT_ENUM, [
   "raw", StringRaw
 ]);
 
 // Set up the non-enumerable functions on the String prototype object.
 utils.InstallFunctions(GlobalString.prototype, DONT_ENUM, [
+  "valueOf", StringValueOf,
+  "toString", StringToString,
   "codePointAt", StringCodePointAt,
   "concat", StringConcat,
   "endsWith", StringEndsWith,
   "includes", StringIncludes,
   "indexOf", StringIndexOf,
   "lastIndexOf", StringLastIndexOf,
   "localeCompare", StringLocaleCompareJS,
   "match", StringMatchJS,
   "normalize", StringNormalize,
   "repeat", StringRepeat,
@@ skipping 33 matching lines @@
   to.StringLastIndexOf = StringLastIndexOf;
   to.StringMatch = StringMatchJS;
   to.StringReplace = StringReplace;
   to.StringSlice = StringSlice;
   to.StringSplit = StringSplitJS;
   to.StringSubstr = StringSubstr;
   to.StringSubstring = StringSubstring;
 });
 
 })