Add constructors to all the event classes.

client/html/src/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 factory MouseEventWrappingImplementation {
 
-interface MouseEvent extends UIEvent {
+  MouseEvent(String type, Window view, int detail, int screenX, int screenY,
+      int clientX, int clientY, int button, [bool canBubble, bool cancelable,
+      bool ctrlKey, bool altKey, bool shiftKey, bool metaKey,
+      EventTarget relatedTarget]);
 
   bool get altKey();
 
   int get button();
 
   int get clientX();
 
   int get clientY();
 
   bool get ctrlKey();
@@ skipping 12 matching lines @@
 
   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);
 }