Support factory methods.

frog/tests/leg_only/src/ListFactoryTest.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+void expectEquals(var expected, var actual) {
+  if (expected != actual) {
+    print("Actual does not match expected");
+    throw actual;
+  }
+}
+
+main() {
+  var a = new List(4);
+  expectEquals(4, a.length);
+  a[0] = 42;
+  a[1] = 43;
+  a[2] = 44;
+  a[3] = 45;
+  for (int i = 0; i < a.length; i++) {
+    expectEquals(42 + i, a[i]);
+  }
+}