Must be on Chrome Canary 78.0.3899.1 or higher for this to work.
Click on "Induce main thread jank" and try to scroll by dragging the thumb (or by clicking on the scrollbar arrows/track).
Notice that the scrolling is extremely janky.
Now enable "Compositor threaded scrollbar scrolling" from about:flags and try the same. (Please note that there are still some
outstanding bugs that are actively being worked on).