Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/generics_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 test.type_arguments_test;
 
+@MirrorsUsed(targets: "test.type_arguments_test")
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 import 'generics_helper.dart';
 
 class A<T> {}
 class Z<T> {}
 class B extends A {}
 class C
     extends A<num, int>  /// 01: static type warning
@@ skipping 136 matching lines @@
     });
   });
 
   Expect.equals(reflectClass(A).typeVariables[0].owner, reflectClass(A));
   Expect.equals(reflectClass(Z).typeVariables[0].owner, reflectClass(Z));
   Expect.notEquals(reflectClass(A).typeVariables[0],
                    reflectClass(Z).typeVariables[0]);
   Expect.equals(reflectClass(A).typeVariables[0],
                 reflectClass(A).typeVariables[0]);
 }