Active tab scrolls out of view when opening many background tabs

Copied and edited from Tab Center Redux Github page.

Steps to reproduce

1. Go to any webpage that contains links
2. Open many links in new background tabs so that they take up more vertical space than what is available

Actual results

The selected tab gets bumped out of view (after it's reached the top) when opening too many tabs

Expected results

• The selected tab should remain visible, no higher than the top of the sidebar
• Visual, animated indicator that new background tabs have been opened out of view