Revert of [intrinsic] Drop the %_ValueOf intrinsic.

src/js/symbol.js

 // Copyright 2013 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) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 14 matching lines @@
 var toPrimitiveSymbol = utils.ImportNow("to_primitive_symbol");
 var toStringTagSymbol = utils.ImportNow("to_string_tag_symbol");
 var unscopablesSymbol = utils.ImportNow("unscopables_symbol");
 
 utils.Import(function(from) {
   MakeTypeError = from.MakeTypeError;
 });
 
 // -------------------------------------------------------------------
 
+// 19.4.3.4 Symbol.prototype [ @@toPrimitive ] ( hint )
+function SymbolToPrimitive(hint) {
+  if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
+    throw MakeTypeError(kIncompatibleMethodReceiver,
+                        "Symbol.prototype [ @@toPrimitive ]", this);
+  }
+  return %_ValueOf(this);
+}
+
+
+function SymbolToString() {
+  if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
+    throw MakeTypeError(kIncompatibleMethodReceiver,
+                        "Symbol.prototype.toString", this);
+  }
+  return %SymbolDescriptiveString(%_ValueOf(this));
+}
+
+
+function SymbolValueOf() {
+  if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
+    throw MakeTypeError(kIncompatibleMethodReceiver,
+                        "Symbol.prototype.valueOf", this);
+  }
+  return %_ValueOf(this);
+}
+
+
 function SymbolFor(key) {
   key = TO_STRING(key);
   var registry = %SymbolRegistry();
   if (IS_UNDEFINED(registry.for[key])) {
     var symbol = %CreateSymbol(key);
     registry.for[key] = symbol;
     registry.keyFor[symbol] = key;
   }
   return registry.for[key];
 }
@@ skipping 18 matching lines @@
   "toPrimitive", toPrimitiveSymbol,
   "toStringTag", toStringTagSymbol,
   "unscopables", unscopablesSymbol,
 ]);
 
 utils.InstallFunctions(GlobalSymbol, DONT_ENUM, [
   "for", SymbolFor,
   "keyFor", SymbolKeyFor
 ]);
 
+%AddNamedProperty(
+    GlobalSymbol.prototype, toStringTagSymbol, "Symbol", DONT_ENUM | READ_ONLY);
+
+utils.InstallFunctions(GlobalSymbol.prototype, DONT_ENUM | READ_ONLY, [
+  toPrimitiveSymbol, SymbolToPrimitive
+]);
+
+utils.InstallFunctions(GlobalSymbol.prototype, DONT_ENUM, [
+  "toString", SymbolToString,
+  "valueOf", SymbolValueOf
+]);
+
+// -------------------------------------------------------------------
+// Exports
+
+utils.Export(function(to) {
+  to.SymbolToString = SymbolToString;
 })
+
+})