…ates. (servo#45655)
Since we have layout query APIs that can skip performing any layout, we
need a way to ensure that any pending layout changes have actually been
processed before those queries are used. If a page contains any
intersection observers, we force a reflow; if no more layout changes
occur within this task then the final reflow operation that updates the
rendering should just skip all of the work that was already done.
Testing: New passing tests.
Fixes: servo#45632
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Signed-off-by: Josh Matthews <josh@joshmatthews.net>