Do *ALL* mobile/touch browsers have “invisible” scrollbars in scrollable areas?

Usually in browsers in touch devices, in scrollable areas, a scrollbar only appears when a user touches it and starts scrolling by moving their finger (in some it never appears at all).

Is this something I can count on 100% to be implemented in ALL mobile/touch browsers? (i.e. none will show an always-visible scrollbar by default) I need to know, for a design decision.