Add constructors to all the event classes.

client/html/src/WheelEventWrappingImplementation.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 WheelEventWrappingImplementation extends UIEventWrappingImplementation implements WheelEvent {
   WheelEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
+  factory WheelEventWrappingImplementation(int deltaX, int deltaY, Window view,
+      int screenX, int screenY, int clientX, int clientY, [bool ctrlKey = false,
+      bool altKey = false, bool shiftKey = false, bool metaKey = false]) {
+    var e = dom.document.createEvent("WheelEvent");
+    e.initWheelEvent(deltaX, deltaY, LevelDom.unwrap(view), screenX, screenY,
+        clientX, clientY, ctrlKey, altKey, shiftKey, metaKey);
+    return LevelDom.wrapWheelEvent(e);
+  }
+
   bool get altKey() { return _ptr.altKey; }
 
   int get clientX() { return _ptr.clientX; }
 
   int get clientY() { return _ptr.clientY; }
 
   bool get ctrlKey() { return _ptr.ctrlKey; }
 
   bool get metaKey() { return _ptr.metaKey; }
 
   int get offsetX() { return _ptr.offsetX; }
 
   int get offsetY() { return _ptr.offsetY; }
 
   int get screenX() { return _ptr.screenX; }
 
   int get screenY() { return _ptr.screenY; }
 
   bool get shiftKey() { return _ptr.shiftKey; }
 
   int get wheelDelta() { return _ptr.wheelDelta; }
 
   int get wheelDeltaX() { return _ptr.wheelDeltaX; }
 
   int get wheelDeltaY() { return _ptr.wheelDeltaY; }
 
   int get x() { return _ptr.x; }
 
   int get y() { return _ptr.y; }
-
-  void initWheelEvent(int wheelDeltaX, int wheelDeltaY, Window view, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey) {
-    _ptr.initWheelEvent(wheelDeltaX, wheelDeltaY, LevelDom.unwrap(view), screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey, metaKey);
-    return;
-  }
 }