Add constructors to all the event classes.

client/html/generated/src/wrapping/_AnimationEventWrappingImplementation.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.
-
-class AnimationEventWrappingImplementation extends EventWrappingImplementation implements AnimationEvent {
-  AnimationEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  String get animationName() { return _ptr.animationName; }
-
-  num get elapsedTime() { return _ptr.elapsedTime; }
-
-  void initWebKitAnimationEvent(String typeArg, bool canBubbleArg, bool cancelableArg, String animationNameArg, num elapsedTimeArg) {
-    _ptr.initWebKitAnimationEvent(typeArg, canBubbleArg, cancelableArg, animationNameArg, elapsedTimeArg);
-    return;
-  }
-}