Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/abstract_class_test.dart

 // Copyright (c) 2014, 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.abstract_class_test;
 
+@MirrorsUsed(targets: "test.abstract_class_test")
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 void main() {
   testSimple();
   testFunctionType();
   testFakeFunction();
   testGeneric();
   testAnonMixinApplication();
   testNamedMixinApplication();
@@ skipping 143 matching lines @@
   {
   // Mixin is abstract.
   Expect.isFalse(reflectClass(ConcreteNamedMA).isAbstract); /// 00: ok
   Expect.isFalse(reflectClass(ConcreteNamedMA).superclass.isAbstract); /// 00: ok
 
   // Mixin is concrete.
   Expect.isFalse(reflectClass(ConcreteNamedMA2).isAbstract);
   Expect.isFalse(reflectClass(ConcreteNamedMA2).superclass.isAbstract);
   }
 }