Added back helper file accidentally deleted during test block 219 migration.

tests/lib/mirrors/constructor_private_name_test.dart

-// Copyright (c) 2013, 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.constructors_test;
-
-// Regression test for C1 bug.
-
-@MirrorsUsed(targets: "test.constructors_test")
-import 'dart:mirrors';
-
-import 'package:expect/expect.dart';
-
-class Foo {
-  Foo._private();
-}
-
-class _Foo {
-  _Foo._private();
-}
-
-main() {
-  ClassMirror fooMirror = reflectClass(Foo);
-  Symbol constructorName =
-      (fooMirror.declarations[#Foo._private] as MethodMirror).constructorName;
-  fooMirror.newInstance(constructorName, []);
-
-  ClassMirror _fooMirror = reflectClass(_Foo);
-  constructorName =
-      (_fooMirror.declarations[#_Foo._private] as MethodMirror).constructorName;
-  _fooMirror.newInstance(constructorName, []);
-}