Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/method_mirror_name_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 lib;
+
+@MirrorsUsed(targets: "lib")
 import "dart:mirrors";
 
 import "package:expect/expect.dart";
 import "stringify.dart";
 
 doNothing42() {}
 
 main() {
   // Regression test for http://www.dartbug.com/6335
   var closureMirror = reflect(doNothing42);
   Expect.equals(stringifySymbol(closureMirror.function.simpleName),
                 "s(doNothing42)");
 }