Revert "Fix use scrollTop instead of _firstVisibleIndex to keep scroller position when"
Revert "Fix use scrollTop instead of _firstVisibleIndex to keep scroller position when"

This reverts commit a19f73f49967d10bb2e8bd7cf8182f0b1af9bf8c.

vaadin/vaadin-grid,vaadin/components,Peppe/vaadin-grid,vaadin/components,vaadin/components,Peppe/vaadin-grid,vaadin/vaadin-grid