 	
 	//--------------------------------------------------------------------------
 	//
-	//  Computing the Visible Column Widths
+	//  Updating the GridDimensions' typicalCell sizes and columnWidths
 	//
 	//-------------------------------------------------------------------------- 
 	
-	private const columnIndices:Vector.<int> = new Vector.<int>(0);
-	private const columnWidths:Vector.<Number> = new Vector.<Number>(0);
-	
-	/**
+    /**
 	 *  @private
 	 *  Use the specified GridColumn's itemRenderer (IFactory) to create a temporary
 	 *  item renderer.   The returned item renderer must be freed, with freeGridElement(),

        
        const scrollX:Number = horizontalScrollPosition;
        const scrollY:Number = verticalScrollPosition;
		updateVisibleColumnWidths(scrollX, scrollY, unscaledWidth, unscaledHeight);
        layoutItemRenderers(grid.itemRendererGroup, scrollX, scrollY, unscaledWidth, unscaledHeight);
        
        // Layout the row backgrounds

        if (!grid)
            return;
        
        // Layout the item renderers and compute new values for visibleRowIndices et al
        
        oldVisibleRowIndices = visibleRowIndices;
