IE 10/11/Edge custom control indicators in a parent element with column-count do not render on the last column

[mattywong]

• Operating system and version (Windows, macOS, Android, iOS, Win10 Mobile)
  Windows 10
• Browser and version (Chrome, Firefox, Safari, IE, MS Edge, Opera 15+, Android Browser)
  Reproduced on IE Edge, IE 11 and IE 10
• Reduced test case and suggested fix using CodePen or JS Bin

Screenshot of issue:

Codepen reproduction:
https://codepen.io/mattywong/full/NWWajYJ

Seems like the fix is to create a new stacking context on custom-control to get it rendering correctly (ideally z-index, though transform and opacity will also create a new stacking context).

[mdo]

Confirmed this is an issue, and that z-index: 1 on the .custom-check resolves the issue. Unsure what other potential problems that introduces though.

[XhmikosR]

Fixed in #30810