[css-break] Fragmented out-of-flow contained by box with cloned borders

[mstensho]

Spec: https://drafts.csswg.org/css-break/#break-decoration

Are out-of-flow positioned elements expected to steer clear of cloned borders in the containing block chain, or should they just overlap?

<div style="columns:3; column-fill:auto; height:100px;">
  <div style="position:relative; box-decoration-break:clone; height:160px; border:10px solid;">
    <div style="position:absolute; top:0; right:0; width:20px; height:250px; background:cyan;"></div>
  </div>
</div>

Firefox thinks so. In a way, this seems reasonable, since we're talking about out-of-flow. Then again, contained out-of-flow elements respect block fragmentation, and cloned box decorations sort of shrink the fragmentainer space available to descendants.

Cloned block edge box decorations aren't implemented by any others at the moment that I'm aware of (well, PrinceXML has it, but they don't fragment OOFs at all, it seems).