             rendererHeights[renderer.column.columnIndex] = renderer.getPreferredBoundsHeight();
         }
         
-        const columns:IList = grid.columns;
+        const columns:IList = columns;
         rendererHeights.length = (columns) ? columns.length : 0;
         
         var maxRendererHeight:Number = 0;

    {
        const columnHeaderGroup:GridColumnHeaderGroup = columnHeaderGroup;
        const grid:Grid = grid;
        
        if (!columnHeaderGroup || !grid || !grid.columns)
            return -1; 
        
        const paddingLeft:Number = columnHeaderGroup.getStyle("paddingLeft");

        const paddingTop:Number = columnHeaderGroup.getStyle("paddingTop");
        const paddingBottom:Number = columnHeaderGroup.getStyle("paddingBottom");
        
        const columns:IList = columns;
        const columnsLength:int = (columns) ? columns.length : 0;
        const lastVisibleColumnIndex:int = grid.getPreviousVisibleColumnIndex(columnsLength);
        const rendererY:Number = paddingTop;
