Add constructors to all the event classes.

client/html/generated/src/wrapping/_MutationEventWrappingImplementation.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 MutationEventWrappingImplementation extends EventWrappingImplementation implements MutationEvent {
-  MutationEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  int get attrChange() { return _ptr.attrChange; }
-
-  String get attrName() { return _ptr.attrName; }
-
-  String get newValue() { return _ptr.newValue; }
-
-  String get prevValue() { return _ptr.prevValue; }
-
-  Node get relatedNode() { return LevelDom.wrapNode(_ptr.relatedNode); }
-
-  void initMutationEvent(String type, bool canBubble, bool cancelable, Node relatedNode, String prevValue, String newValue, String attrName, int attrChange) {
-    _ptr.initMutationEvent(type, canBubble, cancelable, LevelDom.unwrap(relatedNode), prevValue, newValue, attrName, attrChange);
-    return;
-  }
-}