Looks like we're not aligning baseline between items in the outer grid, and items inside the subgrid.
<rdar://problem/89219711>
Filed https://github.com/w3c/csswg-drafts/issues/7078 since the spec doesn't really describe what to do here.
The second sub-test here uses 'last baseline', so we'll need to fix bug 235005 for this test to pass.