There are three types of scrolling: non-fast scrolling, surrogate-driven composited scrolling, and client-driven composited scrolling. Make sure you test this page with and without overlay scrollbars.

Functionality to test: wheel scroll, drag scroll (vertical and horizontal), scrolling as div moves, scrolling of main window, resizing scrollers by dragging scroll corner.

Surrogate repaints the region on every scroll. Client does no compositing work; it just applies paint updates. This is the slowest form of scrolling.

The transform on this div is axis-preserving, thus the layer should be client-driven composited scrolling layer.