Bug 1709975 [wpt PR 28882] - [LayoutNG] Allow spanners inside a transform, a=testonly

Bug 1709975 [wpt PR 28882] - [LayoutNG] Allow spanners inside a transform, a=testonly

Automatic update from web-platform-tests
[LayoutNG] Allow spanners inside a transform

Previously, CanContainSpannerInParentFragmentationContext() would not
allow spanners that are the descendant of a transform. However, the
containing block chain now goes directly from the column spanner
to the multicol container for an NG multicol. Thus, it is safe to
allow a spanner to be a true column spanner if it is a descendant of
a transform (in the case that the multicol is an NG object).

The web test that was added to test the old behavior has been removed
and a new test has been added to test the new behavior.

Bug: 1196727
Change-Id: I908d4fdfc6ce090187dedbc2d9488b1c09bfa989
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2876245
Commit-Queue: Alison Maher <almaher@microsoft.com>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#885554}

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wpt-commits: b78f4000bde8da4e83963200026fa411923f8a2a
wpt-pr: 28882