Use new.target in favor of %_IsConstructCall intrinsic (1).

src/js/weak-collection.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) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 11 matching lines @@
 utils.Import(function(from) {
   GetExistingHash = from.GetExistingHash;
   GetHash = from.GetHash;
   MakeTypeError = from.MakeTypeError;
 });
 
 // -------------------------------------------------------------------
 // Harmony WeakMap
 
 function WeakMapConstructor(iterable) {
-  if (!%_IsConstructCall()) {
+  if (IS_UNDEFINED(new.target)) {
     throw MakeTypeError(kConstructorNotFunction, "WeakMap");
   }
 
   %WeakCollectionInitialize(this);
 
   if (!IS_NULL_OR_UNDEFINED(iterable)) {
     var adder = this.set;
     if (!IS_CALLABLE(adder)) {
       throw MakeTypeError(kPropertyNotFunction, 'set', this);
     }
@@ skipping 68 matching lines @@
   "get", WeakMapGet,
   "set", WeakMapSet,
   "has", WeakMapHas,
   "delete", WeakMapDelete
 ]);
 
 // -------------------------------------------------------------------
 // Harmony WeakSet
 
 function WeakSetConstructor(iterable) {
-  if (!%_IsConstructCall()) {
+  if (IS_UNDEFINED(new.target)) {
     throw MakeTypeError(kConstructorNotFunction, "WeakSet");
   }
 
   %WeakCollectionInitialize(this);
 
   if (!IS_NULL_OR_UNDEFINED(iterable)) {
     var adder = this.add;
     if (!IS_CALLABLE(adder)) {
       throw MakeTypeError(kPropertyNotFunction, 'add', this);
     }
@@ skipping 49 matching lines @@
                   DONT_ENUM | READ_ONLY);
 
 // Set up the non-enumerable functions on the WeakSet prototype object.
 utils.InstallFunctions(GlobalWeakSet.prototype, DONT_ENUM, [
   "add", WeakSetAdd,
   "has", WeakSetHas,
   "delete", WeakSetDelete
 ]);
 
 })