Align GetIterator with ES6 spec

src/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.
 
 "use strict";
 
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $Array = global.Array;
 
 var $WeakMap = global.WeakMap;
 var $WeakSet = global.WeakSet;
 
 
 // -------------------------------------------------------------------
 // Harmony WeakMap
 
 function WeakMapConstructor(iterable) {
   if (!%_IsConstructCall()) {
     throw MakeTypeError('constructor_not_function', ['WeakMap']);
   }
 
   var iter, adder;
 
   if (!IS_NULL_OR_UNDEFINED(iterable)) {
-    iter = GetIterator(ToObject(iterable));
+    iter = GetIterator(iterable);
     adder = this.set;
     if (!IS_SPEC_FUNCTION(adder)) {
       throw MakeTypeError('property_not_function', ['set', this]);
     }
   }
 
   %WeakCollectionInitialize(this);
 
   if (IS_UNDEFINED(iter)) return;
 
@@ skipping 86 matching lines @@
 // Harmony WeakSet
 
 function WeakSetConstructor(iterable) {
   if (!%_IsConstructCall()) {
     throw MakeTypeError('constructor_not_function', ['WeakSet']);
   }
 
   var iter, adder;
 
   if (!IS_NULL_OR_UNDEFINED(iterable)) {
-    iter = GetIterator(ToObject(iterable));
+    iter = GetIterator(iterable);
     adder = this.add;
     if (!IS_SPEC_FUNCTION(adder)) {
       throw MakeTypeError('property_not_function', ['add', this]);
     }
   }
 
   %WeakCollectionInitialize(this);
 
   if (IS_UNDEFINED(iter)) return;
 
@@ skipping 56 matching lines @@
 
   // Set up the non-enumerable functions on the WeakSet prototype object.
   InstallFunctions($WeakSet.prototype, DONT_ENUM, $Array(
     "add", WeakSetAdd,
     "has", WeakSetHas,
     "delete", WeakSetDelete
   ));
 }
 
 SetUpWeakSet();