Add constructors to all the event classes.

client/html/generated/src/wrapping/_OverflowEventWrappingImplementation.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 OverflowEventWrappingImplementation extends EventWrappingImplementation implements OverflowEvent {
-  OverflowEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  bool get horizontalOverflow() { return _ptr.horizontalOverflow; }
-
-  int get orient() { return _ptr.orient; }
-
-  bool get verticalOverflow() { return _ptr.verticalOverflow; }
-
-  void initOverflowEvent(int orient, bool horizontalOverflow, bool verticalOverflow) {
-    _ptr.initOverflowEvent(orient, horizontalOverflow, verticalOverflow);
-    return;
-  }
-}