This reduces the amount of work necessary when running layout, by making
restyle information optional in the `ReflowRequest`. When restyling
isn't
necessary, the option is `None`.
Testing: This shouldn't change any observable behavior and thus is
covered
by existing WPT tests.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>