Default scrollbar visible when slider with border.

[com2]

I wanted to make a transparent slider with border, but that causes the default scrollbar to appears when slider reaches the bottom end.

To reproduce with inspector simply add to the demo:

.scroll {
border: thin solid;
}

Then scroll down until the end the left column text to see the default scrollbar appearing. I saw this with both Firefox 60.0.2 and Chrome 68.0.3440.106