Implement ES6 @@isConcatSpreadable

src/harmony-array.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 124 matching lines @@
   var array = IS_SPEC_FUNCTION(constructor) ? new constructor(length) : [];
   for (var i = 0; i < length; i++) {
     %AddElement(array, i, %_Arguments(i), NONE);
   }
   array.length = length;
   return array;
 }
 
 // -------------------------------------------------------------------
 
+function HarmonyArrayExtendSymbolPrototype() {
+  %CheckIsBootstrapping();
+
+  InstallConstants($Symbol, $Array(
+    // TODO(dslomov, caitp): Move to symbol.js when shipping
+   "isConcatSpreadable", symbolIsConcatSpreadable
+  ));
+}
+
+HarmonyArrayExtendSymbolPrototype();
+
 function HarmonyArrayExtendArrayPrototype() {
   %CheckIsBootstrapping();
 
   // Set up non-enumerable functions on the Array object.
   InstallFunctions($Array, DONT_ENUM, $Array(
     "of", ArrayOf
   ));
 
   // Set up the non-enumerable functions on the Array prototype object.
   InstallFunctions($Array.prototype, DONT_ENUM, $Array(
     "find", ArrayFind,
     "findIndex", ArrayFindIndex,
     "fill", ArrayFill
   ));
 }
 
 HarmonyArrayExtendArrayPrototype();