Use existing test for reflectClass(List).createInstance(...)

tests/lib/mirrors/constructor_optional_args_test.dart

 // Copyright (c) 2016, 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.
 
 library test.constructor_test;
 
 @MirrorsUsed(targets: const [A])
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 class A {
   factory A([x, y]) = B;
   factory A.more([x, y]) = B.more;
   factory A.oneMore(x, [y]) = B.more;
 }
 
 class B implements A {
   final _x, _y, _z;
 
-  B([x = 'x', y = 'y']) : _x = x, _y = y;
+  B([x = 'x', y = 'y']) : _x = x, _y = y, _z = null;
 
   B.more([x = 'x', y = 'y', z = 'z']) : _x = x, _y = y, _z = z;
 
   toString() => 'B(x=$_x, y=$_y, z=$_z)';
 }
 
 
 main() {
   var d1 = new A(1);
   Expect.equals('B(x=1, y=y, z=null)', '$d1', 'direct 1');
@@ skipping 18 matching lines @@
   Expect.equals('B(x=x, y=y, z=z)', '$m1', 'more 1');
   Expect.equals('B(x=1, y=y, z=z)', '$m2', 'more 2');
   Expect.equals('B(x=2, y=3, z=z)', '$m3', 'more 3');
 
   var o1 = cm.newInstance(const Symbol('oneMore'), [1]).reflectee;
   var o2 = cm.newInstance(const Symbol('oneMore'), [2, 3]).reflectee;
 
   Expect.equals('B(x=1, y=y, z=z)', '$o1', 'oneMore one arg');
   Expect.equals('B(x=2, y=3, z=z)', '$o2', 'oneMore two args');
 }