Fixing TransitionEnd event.

tests/html/transition_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 transition_event_test;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_individual_config.dart';
+import 'dart:html';
+
+main() {
+  useHtmlIndividualConfiguration();
+
+  group('supported', () {
+    test('supported', () {
+      expect(CssStyleDeclaration.supportsTransitions, true);
+    });
+  });
+
+  group('functional', () {
+    test('transitionEnd', () {
+      if (CssStyleDeclaration.supportsTransitions) {
+        var element = new DivElement();
+        document.body.append(element);
+
+        element.style.opacity = '0';
+        element.style.width = '100px';
+        element.style.height = '100px';
+        element.style.background = 'red';
+        element.style.transition = 'opacity .1s';
+
+        window.setTimeout(expectAsync0(() {
+          element.onTransitionEnd.first.then(expectAsync1((e) {
+            expect(e is TransitionEvent, isTrue);
+            expect(e.propertyName, 'opacity');
+          }));
+
+          element.style.opacity = '1';
+        }), 100);
+      }
+    });
+  });
+}