Testing on a ChromeOS laptop...

1. Go to https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.webkit%2FWebKit_Win10%2F21483%2F%2B%2Frecipes%2Fsteps%2Fwebkit_tests%2F0%2Fstdout
2. Wait for it to load.
3. Scroll using the thumb 9/10ths of the way down the page.
4. Stop Scrolling
5. Try dragging the scroll thumb again. It doesn't move.