[css-anchor-position-1] anchor-position-grid-001.html relies on unspecified grid behaviour and should be removed

[dshin-moz]

Test List

Remove: /css/css-anchor-position/anchor-position-grid-001.html

Rationale

As per investigation by @dholbert from Gecko side, the test seems to rely on behaviour not specified by the spec (Fragmenting grid-item row-wise).

[dholbert]

behaviour not specified by the spec (Fragmenting grid-item row-wise).

Specifically, the test relies on fragmenting a grid (and its items) in the middle of a grid row; and the CSS grid "Fragmenting Grid Layout" section does not specify that an individual row can be fragmented partway through its block-size, or how that works.

That spec section says "The exact layout of a fragmented grid container is not defined in this level of Grid Layout" and then lays out some basic requirements, including that there are break opportunities between rows (but doesn't mention anything about break opportunities within rows).