Enable ES6 iteration by default

test/mjsunit/es6/string-iterator.js

 // Copyright 2014 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.
 
-// Flags: --harmony-iteration
-
 
 function TestStringPrototypeIterator() {
   assertTrue(String.prototype.hasOwnProperty(Symbol.iterator));
   assertFalse("".hasOwnProperty(Symbol.iterator));
   assertFalse("".propertyIsEnumerable(Symbol.iterator));
 }
 TestStringPrototypeIterator();
 
 
 function assertIteratorResult(value, done, result) {
@@ skipping 65 matching lines @@
 TestForOf();
 
 
 function TestNonOwnSlots() {
   var iterator = ""[Symbol.iterator]();
   var object = {__proto__: iterator};
 
   assertThrows(function() { object.next(); }, TypeError);
 }
 TestNonOwnSlots();