Add constructors to all the event classes.

client/html/generated/src/interface/MouseEvent.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.
-
-interface MouseEvent extends UIEvent {
-
-  bool get altKey();
-
-  int get button();
-
-  int get clientX();
-
-  int get clientY();
-
-  bool get ctrlKey();
-
-  Node get fromElement();
-
-  bool get metaKey();
-
-  int get offsetX();
-
-  int get offsetY();
-
-  EventTarget get relatedTarget();
-
-  int get screenX();
-
-  int get screenY();
-
-  bool get shiftKey();
-
-  Node get toElement();
-
-  int get x();
-
-  int get y();
-
-  void initMouseEvent(String type, bool canBubble, bool cancelable, Window view, int detail, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, int button, EventTarget relatedTarget);
-}