Relax the deltaX/Y/Z types in WheelEvent constructor

tools/dom/templates/html/impl/impl_WheelEvent.darttemplate

 // Copyright (c) 2012, 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.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 
   factory WheelEvent(String type,
-      {Window view, int deltaX: 0, int deltaY: 0, int deltaZ: 0,
+      {Window view, num deltaX: 0, num deltaY: 0, num deltaZ: 0,
       int deltaMode: 0,
       int detail: 0, int screenX: 0, int screenY: 0, int clientX: 0,
       int clientY: 0, int button: 0, bool canBubble: true,
       bool cancelable: true, bool ctrlKey: false, bool altKey: false,
       bool shiftKey: false, bool metaKey: false, EventTarget relatedTarget}) {
 
     var options = {
       'view': view,
       'deltaMode': deltaMode,
       'deltaX': deltaX,
@@ skipping 139 matching lines @@
    * [deltaMode].
    *
    * See also:
    *
    * * [WheelEvent.deltaY](http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#events-WheelEvent-deltaY) from the W3C.
    */
   @DomName('WheelEvent.deltaY')
   num get deltaY => _deltaY;
 $endif
 }