[css-tables] border-radius in collapsed mode

[gregwhitworth]

Compat Issues: No

Description:
The behavior currently specified in CSS 2.1 is not implemented by anyone.

The simplest path to interop is to forbid the behavior completely.

Proposed Option:
Border-radius should be entirely ignored in collapsed-mode, on both table-root and table-cells.

CSS 2.1 Option:
Border-radius should apply on the table-root, but its extent cannot be bigger than the cell forming the corner

Testcases:
https://jsfiddle.net/wazhrfe3/2/

Browsers Passing Test:
Chrome | Firefox | Opera | Safari

[FremyCompany]

The CSSWG resolved this issue during TPAC2016.

Border-radius should have no effect on tables in collapsed mode.

[fantasai]

This isn't a CSS2.1 issue because CSS2.1 didn't have border-radius. :)