merge_pr_50509

Ensure atomic style change events for ElementLayoutUpgrade

If an old style is stored in the PostStyleUpdateScope, it means we need
to perform layout to ensure style change events are atomic for a given
element.

Also fixed some spec links in tests.

Bug: 393513318, 344506496

Change-Id: I49aa1e5a2f9264e1fefbf2898d97e44116a98f3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6231931
Reviewed-by: Anders Hartvoll Ruud [email protected]
Commit-Queue: Rune Lillesveen [email protected]
Cr-Commit-Position: refs/heads/main@{#1416092}