      *  @playerversion AIR 1.5
      *  @productversion Flex 4
      */
-    override protected function viewportHorizontalScrollPositionChangeHandler(event:PropertyChangeEvent):void
+    override mx_internal function viewportHorizontalScrollPositionChangeHandler(event:PropertyChangeEvent):void
     {
         if (viewport)
             value = viewport.horizontalScrollPosition;

     *  @playerversion AIR 1.5
     *  @productversion Flex 4
     */
    override protected function viewportContentWidthChangeHandler(event:PropertyChangeEvent):void
    {
        if (viewport)
            maximum = viewport.contentWidth - viewport.width;

     *  @playerversion AIR 1.5
     *  @productversion Flex 4
     */
    override mx_internal function viewportResizeHandler(event:ResizeEvent):void
    {
        if (viewport)
        {
