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

tests/lib/mirrors/delegate_library_test.dart

-// Copyright (c) 2015, 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.delegate_library;
-
-@MirrorsUsed(targets: "test.delegate_library")
-import 'dart:mirrors';
-
-import 'package:expect/expect.dart';
-
-method(a, b, c) => "$a-$b-$c";
-methodWithNamed(a, {b: 'B', c}) => "$a-$b-$c";
-methodWithOpt(a, [b, c = 'C']) => "$a-$b-$c";
-get getter => 'g';
-set setter(x) {
-  field = x * 2;
-  return 'unobservable value';
-}
-
-var field;
-
-class Proxy {
-  var targetMirror;
-  Proxy(this.targetMirror);
-  noSuchMethod(invocation) => targetMirror.delegate(invocation);
-}
-
-main() {
-  var proxy = new Proxy(reflectClass(Proxy).owner);
-  var result;
-
-  Expect.equals('X-Y-Z', proxy.method('X', 'Y', 'Z'));
-
-  Expect.equals('X-B-null', proxy.methodWithNamed('X'));
-  Expect.equals('X-Y-null', proxy.methodWithNamed('X', b: 'Y'));
-  Expect.equals('X-Y-Z', proxy.methodWithNamed('X', b: 'Y', c: 'Z'));
-
-  Expect.equals('X-null-C', proxy.methodWithOpt('X'));
-  Expect.equals('X-Y-C', proxy.methodWithOpt('X', 'Y'));
-  Expect.equals('X-Y-Z', proxy.methodWithOpt('X', 'Y', 'Z'));
-
-  Expect.equals('g', proxy.getter);
-
-  Expect.equals(5, proxy.setter = 5);
-  Expect.equals(10, proxy.field);
-
-  Expect.equals(5, proxy.field = 5);
-  Expect.equals(5, proxy.field);
-}