Fix performance issue in Grid initial render with Footer (#10705)

* Fix performance issue in Grid initial render with Footer

client/src/main/java/com/vaadin/client/connectors/grid/GridConnector.java

@@ -211,10 +211,9 @@ public class GridConnector extends AbstractListingConnector
 
         Grid<JsonObject> grid = getWidget();
 
-        // Remove default headers when initializing Grid widget
-        while (grid.getHeaderRowCount() > 0) {
-            grid.removeHeaderRow(0);
-        }
+        // Trigger early redraw of both grid static sections.
+        grid.setHeaderVisible(!grid.isHeaderVisible());
+        grid.setFooterVisible(!grid.isFooterVisible());
 
         registerRpc(GridClientRpc.class, new GridClientRpc() {
 

uitest/src/main/java/com/vaadin/tests/components/grid/GridManyColumns.java

@@ -22,6 +22,7 @@ public class GridManyColumns extends AbstractTestUI {
                     .setWidth(200);
         }
         grid.setItems(IntStream.range(0, 10).boxed().map(i -> ""));
+        grid.appendFooterRow();
         addComponent(grid);
     }
 }