Add constructors to all the event classes.

client/html/generated/src/wrapping/_ErrorEventWrappingImplementation.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 ErrorEventWrappingImplementation extends EventWrappingImplementation implements ErrorEvent {
-  ErrorEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  String get filename() { return _ptr.filename; }
-
-  int get lineno() { return _ptr.lineno; }
-
-  String get message() { return _ptr.message; }
-
-  void initErrorEvent(String typeArg, bool canBubbleArg, bool cancelableArg, String messageArg, String filenameArg, int linenoArg) {
-    _ptr.initErrorEvent(typeArg, canBubbleArg, cancelableArg, messageArg, filenameArg, linenoArg);
-    return;
-  }
-}