Scroll jank due to touch/wheel handlers demoView on GitHub
InstructionsThe log shows the touch/wheel events which block scrolling (have cancelable=true).
Scroll the page, observing the latency associated with each event.
In Chrome 51+ and Safari 10, the touch/wheel listeners can be marked as passive to keep them from being able to block the scroll.
When working properly (eg. Chrome 49+) this demo will be able to measure both types of jank.
Safari 9+ appears to work well (though only at millisecond precision and with possible issues with NTP skew).