         if (enablePerformanceStatistics)
             startTime = getTimer();
         
-        const validateNowRenderer:IInvalidating = renderer as IInvalidating;
-        const graphicElementRenderer:IGraphicElement = renderer as IGraphicElement;
-        
         if (!isNaN(width) || !isNaN(height))
         {
-            const validateClientRenderer:ILayoutManagerClient = renderer as ILayoutManagerClient
-            if (validateClientRenderer)
-            {
+            if (renderer is ILayoutManagerClient) 
+            {
+                const validateClientRenderer:ILayoutManagerClient = renderer as ILayoutManagerClient;                
                 LayoutManager.getInstance().validateClient(validateClientRenderer, true); // true => skip validateDisplayList()
             }
-            else if (graphicElementRenderer)
-            {
+            else if (renderer is IGraphicElement)
+            {
+                const graphicElementRenderer:IGraphicElement = renderer as IGraphicElement;                
                 graphicElementRenderer.validateProperties();
                 graphicElementRenderer.validateSize();
             }

                    cellHeight = renderer.getPreferredBoundsHeight();
                    gridDimensions.setTypicalCellHeight(columnIndex, cellHeight);
                }
                freeGridElement(renderer);
            }
            

            renderer.setLayoutBoundsSize(width, height);            
        }
        
        renderer.setLayoutBoundsPosition(x, y);

        if (enablePerformanceStatistics)
        {
            var elapsedTime:Number = getTimer() - startTime;
