Add all dart:html tests from the sdk to test/codegen.

test/codegen/lib/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 'package:unittest/unittest.dart';
+import 'package:unittest/html_individual_config.dart';
+import 'dart:html';
+import 'dart:async';
+
+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';
+
+        new Timer(const Duration(milliseconds: 100), expectAsync(() {
+          element.onTransitionEnd.first.then(expectAsync((e) {
+            expect(e is TransitionEvent, isTrue);
+            expect(e.propertyName, 'opacity');
+          }));
+
+          element.style.opacity = '1';
+        }));
+      }
+    });
+  });
+}