      *  @private
      *  Instance of the scrollTip. (There can be only one.)
      */
-    private var scrollTip:ToolTip;
+    private var scrollTip:IToolTip;
 
     /**
      *  @private

            {
                if (scrollTip)
                {
			       	systemManager.topLevelSystemManager.removeChildFromSandboxRoot("toolTipChildren", scrollTip as DisplayObject);
                    scrollTip = null;
                    ToolTipManager.enabled = oldTTMEnabled;
                }


                if (!scrollTip)
                {
                    scrollTip = ToolTipManager.createToolTip("", 0, 0, null, this);
                    scrollThumbMidPoint = scrollBar.scrollThumb.height / 2;
                    oldTTMEnabled = ToolTipManager.enabled;
                    ToolTipManager.enabled = false;
