Bug 1750069 [wpt PR 32369] - Clear fragment item association when any fragments have...

Bug 1750069 [wpt PR 32369] - Clear fragment item association when any fragments have items, a=testonly

Automatic update from web-platform-tests
Clear fragment item association when any fragments have items

Before this change, |ReplaceLayoutResult| clears associations
only when the first fragment has items.

Block fragmentation can create items only for second or later
fragments; e.g.:
  results[0] does not have |NGFragmentItems|.
  results[1] has |NGFragmentItems|.
This patch changes |ReplaceLayoutResult| to clear associations
in such cases.

Also changes |ClearLayoutResults| for the consistency.

Bug: 1283250
Change-Id: I42411bcbfdb2370d58f1360d22846dad6d94dd24
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3386495
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#958855}

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wpt-commits: 7bd2525f16a90829f8f9ea3498dcdf8b433423e5
wpt-pr: 32369