Clean up WheelEvent

tools/dom/templates/html/impl/impl_Element.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;
 
 class _ChildrenElementList extends ListBase<Element>
     implements NodeListWrapper {
   // Raw Element.
   final Element _element;
@@ skipping 926 matching lines @@
    * Static factory designed to expose `mousewheel` events to event
    * handlers that are not necessarily instances of [Element].
    *
    * See [EventStreamProvider] for usage information.
    */
   @DomName('Element.mouseWheelEvent')
   static const EventStreamProvider<WheelEvent> mouseWheelEvent =
       const _CustomEventStreamProvider<WheelEvent>(
         Element._determineMouseWheelEventType);
 
-  static String _determineMouseWheelEventType(EventTarget e) {
-    if (JS('bool', '#.onwheel !== undefined', e)) {
-      // W3C spec, and should be IE9+, but IE has a bug exposing onwheel.
-      return 'wheel';
-    } else if (JS('bool', '#.onmousewheel !== undefined', e)) {
-      // Chrome & IE
-      return 'mousewheel';
-    } else {
-      // Firefox
-      return 'DOMMouseScroll';
-    }
-  }
+  static String _determineMouseWheelEventType(EventTarget e) => 'wheel';
 
   /**
    * Static factory designed to expose `transitionend` events to event
    * handlers that are not necessarily instances of [Element].
    *
    * See [EventStreamProvider] for usage information.
    */
   @DomName('Element.transitionEndEvent')
   static const EventStreamProvider<TransitionEvent> transitionEndEvent =
       const _CustomEventStreamProvider<TransitionEvent>(
@@ skipping 608 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }