While scrolling via trackpad or mousewheel, we previously sent mouse position updates every 100ms. On pages with heavy mouse handlers or :hover styles, this could cause significant amounts of scroll jank. Sending a mouse position update includes updating :hover styles, and dispatching mousemove, mouseover, mouseenter, mouseleave, and mouseout events. We’re planning to stop sending mouse position updates while scrolling. Instead, we'll trigger this behavior 100ms after scrolling ends.
Docs: https://groups.google.com/a/chromium.org/d/msg/blink-dev/KIoVljZw5fc/EKGAoTeX8CQJ