Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/instantiate_abstract_class_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.instantiate_abstract_class;
 
+@MirrorsUsed(targets: const ["dart.core", AbstractClass])
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 
 assertInstanitationErrorOnGenerativeConstructors(classMirror) {
   classMirror.declarations.values.forEach((decl) {
     if (decl is! MethodMirror) return;
     if (!decl.isGenerativeConstructor) return;
     var args = new List(decl.parameters.length);
     Expect.throws(() => classMirror.newInstance(decl.constructorName, args),
@@ skipping 20 matching lines @@
 class ConcreteClass implements AbstractClass {}
 
 main() {
   assertInstanitationErrorOnGenerativeConstructors(reflectType(num));
   assertInstanitationErrorOnGenerativeConstructors(reflectType(double));
   assertInstanitationErrorOnGenerativeConstructors(reflectType(StackTrace));
 
   assertInstanitationErrorOnGenerativeConstructors(reflectType(AbstractClass));
   runFactoryConstructors(reflectType(AbstractClass));
 }