-mode that
       disagrees with the abspos element's parent. We exercise all 6
       pairwise-mismatching combinations of {htb,vlr,vrl} for the grandparent &
       parent.  For each such pair, we test all three of those same
       writing-modes on the innermost abspos element.

       Note that we use 'data-expected-{height,width}' depending on which axis
       is the block axis for the abspos ".test" element (since that's the
       element whose "block-size: stretch" resolution we're testing).  So fo