This crashed Chrome 84.
Test
Outer is a regular div.
Test
relpos element is a regular div, not flexbox.
Test
Relpos flexbox has a % height descendant. The height of the flexbox grid item is supposed to be definite, allowing the %height flex item to resolve. This fails in chrome because of https://crbug.com/1018439
Test

PASS .relpos 1
PASS .relpos 2
PASS .relpos 3
PASS .relpos 4
PASS .relpos 5
PASS .relpos 6
PASS .relpos 7
PASS .relpos 8