Support factory methods.

frog/tests/leg_only/src/FactoryTest.dart

Index: frog/tests/leg_only/src/FactoryTest.dart
===================================================================
--- frog/tests/leg_only/src/FactoryTest.dart	(revision 0)
+++ frog/tests/leg_only/src/FactoryTest.dart	(revision 0)
@@ -0,0 +1,13 @@
+// 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.
+
+class A {
+  factory A() {
+    return 1;
+  }
+}
+
+main() {
+  Expect.equals(1, new A());
+}