Show scrollbars on iOS when scrolling via Javascript

I would like the vertical scrollbar to be displayed when I call element.scrollTop = <somePosition>;

Here is an example of what I'm trying to achieve: https://plnkr.co/edit/0ls05cCa3XrvrWPO?open=lib%2Fscript.js&preview

If that example is loaded on iOS, when the left box is scrolled, the right box should sync with it. That works just fine, but I need a way for the scrollbar to also show up.

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