workaround for event handlers: don't return StreamSubscription as model

pkg/polymer/test/custom_event_test.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.
 
 library polymer.test.web.custom_event_test;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:polymer/polymer.dart';
+import 'package:template_binding/template_binding.dart' show nodeBind;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
 
 @CustomTag('foo-bar')
 class FooBar extends PolymerElement {
   // A little too much boilerplate?
   static const EventStreamProvider<CustomEvent> fooEvent =
       const EventStreamProvider<CustomEvent>('foo');
   static const EventStreamProvider<CustomEvent> barBazEvent =
@@ skipping 23 matching lines @@
 
 main() {
   initPolymer();
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   test('custom event', () {
     final testComp = query('test-custom-event');
     final fooBar = testComp.fooBar;
+
+    final binding = nodeBind(fooBar).bindings['on-barbaz'];
+    expect(binding, isNotNull, reason: 'on-barbaz event should be bound');
+
+    expect(binding.model is! StreamSubscription, true,
+        reason: 'event bindings should not be a StreamSubscription');
+
     fooBar.fireFoo(123);
     fooBar.fireBarBaz(42);
     fooBar.fireFoo(777);
 
     final events = testComp.events;
     expect(events.length, 3);
     expect(events.map((e) => e[0]), ['foo', 'barbaz', 'foo']);
     expect(events.map((e) => e[1].detail), [123, 42, 777]);
   });
 }