Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/constructor_kinds_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.constructor_kinds_test;
 
+@MirrorsUsed(targets: "test.constructor_kinds_test")
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 class ClassWithDefaultConstructor {}
 
 class Class {
   Class.generativeConstructor();
   Class.redirectingGenerativeConstructor() : this.generativeConstructor();
   factory Class.factoryConstructor() => new Class.generativeConstructor();
   factory Class.redirectingFactoryConstructor() = Class.factoryConstructor;
@@ skipping 85 matching lines @@
   // Expect.isFalse(mm.isRedirectingConstructor);
   // Expect.isTrue(mm.isConstConstructor);
 
   mm = cm.declarations[#Class.constRedirectingFactoryConstructor];
   Expect.isTrue(mm.isConstructor);
   Expect.isFalse(mm.isGenerativeConstructor);
   Expect.isTrue(mm.isFactoryConstructor);
   Expect.isTrue(mm.isRedirectingConstructor);
   Expect.isTrue(mm.isConstConstructor);
 }