Add constructors to all the event classes.

client/html/src/OverflowEvent.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 OverflowEvent extends Event factory OverflowEventWrappingImplementation {
 
-interface OverflowEvent extends Event {
+  OverflowEvent(int orient, bool horizontalOverflow, bool verticalOverflow);
 
   static final int BOTH = 2;
 
   static final int HORIZONTAL = 0;
 
   static final int VERTICAL = 1;
 
   bool get horizontalOverflow();
 
   int get orient();
 
   bool get verticalOverflow();
-
-  void initOverflowEvent(int orient, bool horizontalOverflow, bool verticalOverflow);
 }