bokan@ how should the overlay scrollbar behave when the content of the scrollable area changes? Currently it does hide the scrollbar which seems a little annoying.

Looks like the scrollbar is being recreated each time the timer fires. This is a layout stability issue.

FWIW, there's a simple workaround, split up the current div into one that causes the overflow (and scrollbars) and one that houses the content.

<div style="display: grid; height: 200px">
    <div style="overflow: auto">
      <div style="height: 400px; background-color:#cccccc">
        <div id="test"><!-- CONTENT GOES HERE --></div>
      </div>
    </div>
</div>

Marking as untriaged so layout team actually sees it

Setting the inner html removes all the old content (and thus the auto scrollbar) before creating the new content and, if it still overflows, creates a new scrollbar.

This is by design and working as intended.

Setting overflow to scroll instead preserves the scrollbar across invocations.

I am using Chrome 66.0.3359.117 and I am still seeing the same problem with the workaround suggested in comment 3.

https://jsfiddle.net/dgtmgam9/15/

Yeah, sorry - the overflow: auto div needs to have an explicit height: https://jsfiddle.net/dgtmgam9/20/

Or make the top level div overflow: auto: https://jsfiddle.net/dgtmgam9/19/