Refactor array construction for map, filter

test/mjsunit/regress/regress-544991.js

+// Copyright 2015 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.
+
+var typedArray = new Int8Array(1);
+var saved;
+var called;
+typedArray.constructor = function(x) { called = true; saved = x };
+typedArray.constructor.prototype = Int8Array.prototype;
+typedArray.map(function(){});
+
+// To meet the spec, constructor shouldn't be called directly, but
+// if it is called for now, the argument should be an Array
+assertTrue(called); // Will fail later; when so, delete this test
+assertEquals("Array", saved.constructor.name);