Recently, Chrome has difficulties with 120Hz smooth scrolling. Even on 120hz monitors, scrolling is always 60fps regardless of keyboard, mousewheel, chrome://flags smooth scroll setting, or Chromium Smooth Scroller extension. Internet Explorer 10 and 11 currently does nearly perfectly smooth 120Hz scrolling via the up/down arrow keys.
Blur Busters has filed Issue #310848, now successfully reproduced and assigned to a Chrome developer. Let’s see 120fps @ 120Hz smooth scrolling in Chrome soon.