height:25% in root
0
1
height:25% in 8-line height:auto relpos
2
3
height:auto in relpos
4
5
6
7
height:25% non-abspos in height:auto relpos, so computed height:auto per spec
height:inherit child of the above non-abspos

Result: In all browsers tested, the height:inherit abspos behaves like height:25% rather than height:auto, so it seems that its parent has a computed value of simply 25% rather than auto.