Implement header size calculation for array iterators.

test/mjsunit/regress/regress-674232.js

+// Copyright 2016 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 getRandomProperty(v, rand) { var properties = Object.getOwnPropertyNames(v); var proto = Object.getPrototypeOf(v); if (proto) {; } if ("constructor" && v.constructor.hasOwnProperty()) {; } if (properties.length == 0) { return "0"; } return properties[rand % properties.length]; }
+function __f_11() {
+  var __v_8 = new Array();
+  var __v_9 = __v_8.entries();
+  __v_9.__p_118574531 = __v_9[ 118574531];
+  __v_9.__defineGetter__(getRandomProperty(__v_9, 1442724132), function() {; __v_0[getRandomProperty()] = __v_1[getRandomProperty()]; return __v_9.__p_118574531; });
+}
+function __f_10() {
+  __f_11();
+}
+__f_10();
+__f_10();