Breaking Change: Support @JS at library level

tests/html/js_typed_interop_anonymous_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.
 
+@JS()
 library js_typed_interop_anonymous_test;
 
 import 'dart:html';
 import 'dart:js' as js;
 
 import 'package:js/js.dart';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
 @JS() @anonymous
 class Literal {
   external factory Literal({int x, String y, num z});
 
   external int get x;
   external String get y;
   external num get z;
 }
 
 main() {
   useHtmlConfiguration();
 
   test('simple', () {
     var l = new Literal(x: 3, y: "foo");
     expect(l.x, equals(3));
     expect(l.y, equals("foo"));
     expect(l.z, isNull);
   });
 }