Add constructors to all the event classes.

client/html/generated/src/wrapping/_CompositionEventWrappingImplementation.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 CompositionEventWrappingImplementation extends UIEventWrappingImplementation implements CompositionEvent {
-  CompositionEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  String get data() { return _ptr.data; }
-
-  void initCompositionEvent(String typeArg, bool canBubbleArg, bool cancelableArg, Window viewArg, String dataArg) {
-    _ptr.initCompositionEvent(typeArg, canBubbleArg, cancelableArg, LevelDom.unwrap(viewArg), dataArg);
-    return;
-  }
-}