Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/closurization_equivalence_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 lib;
+
+@MirrorsUsed(targets: "lib")
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 topLevelMethod() {}
 class C {
   static staticMethod() {}
   instanceMethod() {}
 }
 
 main() {
   LibraryMirror thisLibrary = reflectClass(C).owner;
   Expect.equals(thisLibrary.declarations[#topLevelMethod],
                 (reflect(topLevelMethod) as ClosureMirror).function,
                 "topLevel");
 
   Expect.equals(reflectClass(C).declarations[#staticMethod],
                 (reflect(C.staticMethod) as ClosureMirror).function,
                 "static");
 
   Expect.equals(reflectClass(C).declarations[#instanceMethod],
                 (reflect(new C().instanceMethod) as ClosureMirror).function,
                 "instance");
 }