Detect and wrap JS-CustomEvents if applicable. Include created_watcher and

pkg/polymer/test/js_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.events_test;
+
+import 'dart:html';
+import 'dart:js';
+import 'package:polymer/polymer.dart';
+import 'package:unittest/html_config.dart';
+import 'package:unittest/unittest.dart';
+
+@CustomTag('x-test')
+class XTest extends PolymerElement {
+  bool called = false;
+  XTest.created() : super.created();
+
+  void myEventHandler(e, detail, t) {
+    called = true;
+    expect(detail['value'], 42);
+  }
+}
+
+main() => initPolymer().run(() {
+  useHtmlConfiguration();
+  setUp(() => Polymer.onReady);
+
+  test('detail on JS custom events are proxied', () {
+    var element = querySelector('x-test');
+    expect(element.called, isFalse);
+    context.callMethod('fireEvent');
+    expect(element.called, isTrue);
+  });
+});