Add constructors to all the event classes.

client/html/generated/src/wrapping/_CloseEventWrappingImplementation.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 CloseEventWrappingImplementation extends EventWrappingImplementation implements CloseEvent {
-  CloseEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  int get code() { return _ptr.code; }
-
-  String get reason() { return _ptr.reason; }
-
-  bool get wasClean() { return _ptr.wasClean; }
-
-  void initCloseEvent(String typeArg, bool canBubbleArg, bool cancelableArg, bool wasCleanArg, int codeArg, String reasonArg) {
-    _ptr.initCloseEvent(typeArg, canBubbleArg, cancelableArg, wasCleanArg, codeArg, reasonArg);
-    return;
-  }
-}