Add JSNative utility class with static methods methods to efficiently manipulate typed JSInterop ob…

pkg/js/lib/js_util.dart

Index: pkg/js/lib/js_util.dart
diff --git a/pkg/analyzer_cli/test/data/package_with_embedder_yaml/lib/grizzly.dart b/pkg/js/lib/js_util.dart
similarity index 70%
copy from pkg/analyzer_cli/test/data/package_with_embedder_yaml/lib/grizzly.dart
copy to pkg/js/lib/js_util.dart
index d575643598c26036bc0e72a3592eeccc5d6eaf44..1e47e5d4ec7aa6a5c47cd677a27203867c5423b6 100644
--- a/pkg/analyzer_cli/test/data/package_with_embedder_yaml/lib/grizzly.dart
+++ b/pkg/js/lib/js_util.dart
@@ -2,6 +2,7 @@
 // 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 grizzly;
+/// Allows interoperability with Javascript APIs.
+library js_util;
 
-class Bear {}
+export 'dart:js_util';