Breaking Change: Support @JS at library level

tests/html/js_typed_interop_anonymous2_exp_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.
 //
 // SharedOptions=--experimental-trust-js-interop-type-annotations
 
 // Same test as js_typed_interop_anonymous2, but using the
 // --experimental-trust-js-interop-type-annotations flag.
+@JS()
 library js_typed_interop_anonymous2_exp_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
@@ skipping 24 matching lines @@
 main() {
   useHtmlConfiguration();
 
   test('simple', () {
     var b = new B();
     var a = new A(b: b);
     expect(a.b, equals(b));
     expect(b.c, isNull);
   });
 }