When a Node with a pseudo-element style that uses `content: attr()`
has one of its attributes mutated, trigger a reflow starting at that
node. This is a crude implementation, because we currently aren't taking
into account what attributes changed, but at least it works.
Testing: This doesn't have any test changes, but should fix the test
situation described in #40419.
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Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>