avoid addEventListener in Polymer

pkg/polymer/lib/src/events.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.
 
 /// Code from declaration/events.js
 part of polymer;
 
 /// An extension of [polymer_expressions.PolymerExpressions] that adds support
 /// for binding events using `on-eventName` using [PolymerEventBindings].
 // TODO(jmesserly): the JS layering is a bit odd, with polymer-dev implementing
@@ skipping 64 matching lines @@
 
   prepareEventBinding(String path, String name, Node node) {
     if (!_hasEventPrefix(name)) return null;
 
     var eventType = _removeEventPrefix(name);
     var translated = _eventTranslations[eventType];
     eventType = translated != null ? translated : eventType;
 
     return (model, node, oneTime) {
       var handler = getEventHandler(null, node, path);
-      node.addEventListener(eventType, handler);
+      var sub = node.on[eventType].listen(handler);
 
       if (oneTime) return null;
-      return new _EventBindable(node, eventType, handler, path);
+      return new _EventBindable(sub, path);
     };
   }
 }
 
 
 class _EventBindable extends Bindable {
-  final Node _node;
-  final String _eventType;
-  final Function _handler;
+  final StreamSubscription _sub;
   final String _path;
 
-  _EventBindable(this._node, this._eventType, this._handler, this._path);
+  _EventBindable(this._sub, this._path);
 
   // TODO(rafaelw): This is really pointless work. Aside from the cost
   // of these allocations, NodeBind is going to setAttribute back to its
   // current value. Fixing this would mean changing the TemplateBinding
   // binding delegate API.
   get value => '{{ $_path }}';
 
   open(callback) => value;
 
-  void close() => _node.removeEventListener(_eventType, _handler);
+  void close() {
+    if (_sub != null) {
+      _sub.cancel();
+      _sub = null;
+    }
+  }
 }
 
 
 /// Attribute prefix used for declarative event handlers.
 const _EVENT_PREFIX = 'on-';
 
 /// Whether an attribute declares an event.
 bool _hasEventPrefix(String attr) => attr.startsWith(_EVENT_PREFIX);
 
 String _removeEventPrefix(String name) => name.substring(_EVENT_PREFIX.length);
@@ skipping 27 matching lines @@
   return map;
 }();
 
 // Dart note: we need this function because we have additional renames JS does
 // not have. The JS renames are simply case differences, whereas we have ones
 // like doubleclick -> dblclick and stripping the webkit prefix.
 String _eventNameFromType(String eventType) {
   final result = _reverseEventTranslations[eventType];
   return result != null ? result : eventType;
 }