Add constructors to all the event classes.

client/html/src/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) {}
 
+  factory OverflowEventWrappingImplementation(int orient,
+      bool horizontalOverflow, bool verticalOverflow) {
+    var e = dom.document.createEvent("OverflowEvent");
+    e.initOverflowEvent(orient, horizontalOverflow, verticalOverflow);
+    return LevelDom.wrapOverflowEvent(e);
+  }
+
   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;
-  }
 }