Add @jsify annotation. Support automatically proxying Lists and Maps to Dart in Proxies. Support co…

lib/src/metadata.dart

 // Copyright (c) 2014, 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.
 
 /**
  * This library contains the annotations used in js.dart separately so they can
  * be imported into the VM.
  */
 library js.metadata;
 
@@ skipping 20 matching lines @@
  * JsInterface.
  *
  * Classes annotated with @JsProxy() are transformed to add an impementation of
  * all abstract methods defined on superclasses that extend JsInterface.
  */
 class JsProxy {
   final String constructor;
   final bool global;
   const JsProxy({this.constructor, this.global: false});
 }
+
+
+class Jsify {
+  const Jsify();
+}
+
+const jsify = const Jsify();