Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/removed_api_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';
 
 class C {}
 
 expectThrowsNSM(f) {
   Expect.throws(f, (e) => e is NoSuchMethodError);
 }
 
 main() {
@@ skipping 13 matching lines @@
   expectThrowsNSM(() => reflectClass(C).getters);
   expectThrowsNSM(() => reflectClass(C).setters);
   expectThrowsNSM(() => reflectClass(C).variables);
   expectThrowsNSM(() => reflectClass(C).constructors);
 
   expectThrowsNSM(() => MirroredError);
   expectThrowsNSM(() => MirrorException);
   expectThrowsNSM(() => MirroredUncaughtExceptionError);
   expectThrowsNSM(() => MirroredCompilationError);
 }