      *  @see mx.core.IViewport
      *  @see mx.core.IViewport#verticalScrollPosition
      *  @see mx.core.IViewport#getVerticalScrollPositionDelta()
+     *  
+     *  @langversion 3.0
+     *  @playerversion Flash 10
+     *  @playerversion AIR 1.5
+     *  @productversion Flex 4
      */
     override public function step(increase:Boolean = true):void
     {

    /**
     *  Set this scrollbar's maximum to the viewport's contentHeight 
     *  less the viewport height and its pageSize to the viewport's height. 
     */
    override protected function viewportResizeHandler(event:ResizeEvent):void
    {


    /**
     *  The size of the track, which equals the height of the track.
     *  
     *  @langversion 3.0
     *  @playerversion Flash 10
     *  @playerversion AIR 1.5
     *  @productversion Flex 4
     */
    override protected function get trackSize():Number
    {
