Add constructors to all the event classes.

client/html/src/TransitionEvent.dart

 // Copyright (c) 2011, 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.
 
-// WARNING: Do not edit - generated code.
+interface TransitionEvent extends Event factory TransitionEventWrappingImplementation {
 
-interface TransitionEvent extends Event {
+  TransitionEvent(String type, String propertyName, double elapsedTime,
+      [bool canBubble, bool cancelable]);
 
   num get elapsedTime();
 
   String get propertyName();
-
-  void initWebKitTransitionEvent(String typeArg, bool canBubbleArg, bool cancelableArg, String propertyNameArg, num elapsedTimeArg);
 }