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

tests/lib_2/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;
 
 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);
+  dynamic 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);
 }