Update ObjectToString to Harmony-draft algorithm

src/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.
 
 "use strict";
 
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $Array = global.Array;
 
@@ skipping 83 matching lines @@
 
   %SetCode($Symbol, SymbolConstructor);
   %FunctionSetPrototype($Symbol, new $Object());
 
   InstallConstants($Symbol, $Array(
     // TODO(rossberg): expose when implemented.
     // "hasInstance", symbolHasInstance,
     // "isConcatSpreadable", symbolIsConcatSpreadable,
     // "isRegExp", symbolIsRegExp,
     "iterator", symbolIterator,
+    // TODO: Currently defined in harmony-tostring.js --- Move here when shipping

[Dmitry Lomov (no reviews), 2014/10/17 19:29:06]

nit: 80 column lines

[caitp (gmail), 2014/10/17 20:12:13]

Acknowledged.

     // "toStringTag", symbolToStringTag,
     "unscopables", symbolUnscopables
   ));
   InstallFunctions($Symbol, DONT_ENUM, $Array(
     "for", SymbolFor,
     "keyFor", SymbolKeyFor
   ));
 
   %AddNamedProperty($Symbol.prototype, "constructor", $Symbol, DONT_ENUM);
+  %AddNamedProperty(
+      $Symbol.prototype, symbolToStringTag, "Symbol", DONT_ENUM | READ_ONLY);

[Dmitry Lomov (no reviews), 2014/10/17 19:29:06]

Hmm, when --harmony-tostring is turned off, where symbolToStringTag comes from?

Maybe better to move all these prototype modifications to harmony-tostring.js?

[caitp (gmail), 2014/10/17 20:12:13]

It's defined in both harmony-tostring.js and symbol.js --- InternalSymbol will
just return the existing symbol in the well known symbols registry if it already
exists, so this is fine.

It doesn't hurt to define the property regardless of whether the flag is enabled
or not, although I guess it's a bit of extra memory that never gets used if it's
not there

[Dmitry Lomov (no reviews), 2014/10/18 08:41:49]

Oh I see. missed that.
Yes, it is fine

   InstallFunctions($Symbol.prototype, DONT_ENUM, $Array(
     "toString", SymbolToString,
     "valueOf", SymbolValueOf
   ));
 }
 
 SetUpSymbol();
 
 
 function ExtendObject() {
   %CheckIsBootstrapping();
 
   InstallFunctions($Object, DONT_ENUM, $Array(
     "getOwnPropertySymbols", ObjectGetOwnPropertySymbols
   ));
 }
 
 ExtendObject();