[es6] Iterators and generators should "extend" %IteratorPrototype%

src/string-iterator.js

Index: src/string-iterator.js
diff --git a/src/string-iterator.js b/src/string-iterator.js
index c19e808020cee52355bfbfcf28bbd37fd72ee4ef..82493562558a191e0d1ad2cf5df2277f6ac67b10 100644
--- a/src/string-iterator.js
+++ b/src/string-iterator.js
@@ -8,7 +8,6 @@
 
 %CheckIsBootstrapping();
 
-var GlobalObject = global.Object;
 var GlobalString = global.String;
 
 //-------------------------------------------------------------------
@@ -31,12 +30,6 @@ function CreateStringIterator(string) {
 }
 
 
-// 21.1.5.2.2 %StringIteratorPrototype%[@@iterator]
-function StringIteratorIterator() {
-  return this;
-}
-
-
 // 21.1.5.2.1 %StringIteratorPrototype%.next( )
 function StringIteratorNext() {
   var iterator = $toObject(this);
@@ -85,15 +78,12 @@ function StringPrototypeIterator() {
 
 //-------------------------------------------------------------------
 
-%FunctionSetPrototype(StringIterator, new GlobalObject());
+%FunctionSetPrototype(StringIterator, {__proto__: $iteratorPrototype});
 %FunctionSetInstanceClassName(StringIterator, 'String Iterator');
 
 $installFunctions(StringIterator.prototype, DONT_ENUM, [
   'next', StringIteratorNext
 ]);
-$setFunctionName(StringIteratorIterator, symbolIterator);
-%AddNamedProperty(StringIterator.prototype, symbolIterator,
-                  StringIteratorIterator, DONT_ENUM);
 %AddNamedProperty(StringIterator.prototype, symbolToStringTag,
                   "String Iterator", READ_ONLY | DONT_ENUM);