Slow re-render using round border-radius, overflow hidden in Firefox

[louisch]

In Firefox, when dragging the contents of a div with border-radius 50% (so a circle) and overflow: hidden, the browser is slow to re-render, resulting in the content visually overflowing or underflowing for 1~4 seconds before the re-render happens and the content is correctly displayed again.

[donmbelembe]

I was able to reproduce the same error on firefox, it only happens when overflow is set to hidden, I don't know exactly why we get this problem on firefox