Скольжение это 3-4 пальцевый мультитач жест для Mac.

Источник:

http://www.firefoxfacts.com/2014/04/08/firegestures/

Here are the different mouse gestures you can use to execute various commands:

  • Mouse Gestures (Move mouse with holding right-click)
  • Wheel Gestures (Scroll wheel with holding right-click)
  • Rocker Gestures (Left-click with holding right-click and vice versa)
  • Keypress Gestures (Mouse gesture with holding Ctrl / Shift key)
  • Tab Wheel Gestures (Scrolling wheel on the tab bar)
  • Swipe Gestures (3 or 4 fingers multi-touch on Mac’s trackpad)