Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/mirrors_nsm_mismatch_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 test.mirrors_nsm_mistatch;
+library test.mirrors_nsm_mismatch;
 
+@MirrorsUsed(targets: "test.mirrors_nsm_mismatch")
 import 'dart:mirrors';
 import 'mirrors_nsm_test.dart';
 
 topLevelMethod({missing}) {}
 class C {
   C.constructor({missing});
   factory C.redirecting({missing}) = C.constructor;
   static staticMethod({missing}) {}
   instanceMethod({missing}) {}
 }
 
 main() {
   var mirrors = currentMirrorSystem();
-  var libMirror = mirrors.findLibrary(#test.mirrors_nsm_mistatch);
+  var libMirror = mirrors.findLibrary(#test.mirrors_nsm_mismatch);
   expectMatchingErrors(() => libMirror.invoke(#topLevelMethod, [], {#extra: 1}),
                        () => topLevelMethod(extra: 1));
   expectMatchingErrors(() => libMirror.invoke(#topLevelMethod, ['positional']),
                        () => topLevelMethod('positional'));
 
   var classMirror = reflectClass(C);
   expectMatchingErrors(() => classMirror.newInstance(#constructor, [],
                                                      {#extra: 1}),
                        () => new C.constructor(extra: 1));
   expectMatchingErrors(() => classMirror.newInstance(#redirecting, [],
@@ skipping 14 matching lines @@
 
   var instanceMirror = reflect(new C.constructor());
   expectMatchingErrors(() => instanceMirror.invoke(#instanceMethod, [],
                                                    {#extra: 1}),
                        () => instanceMirror.reflectee.instanceMethod(extra: 1));
   expectMatchingErrors(() => instanceMirror.invoke(#instanceMethod,
                                                    ['positional']),
                        () => instanceMirror.reflectee
                                  .instanceMethod('positional'));
 }