In layout calculation within script, Instead of relying on the computed
values for overflow, query the overflow from layout for its used value
to accurately reflect whether an element establish a scroll container.
This query will be used for `IntersectionObserver` as well.
Testing: There are new `IntersectionObserver` WPT failures:
- `intersection-observer/isIntersecting-change-events.html`
- `intersection-observer/containing-block.html`
The failures are more than likely a false positive because intersection
observation steps wasn't supposed to trigger a reflow, but it was
before. It could be caused by the implementation of
`IntersectionObserver` in major UAs being a little bit different from
the spec in the calculation of `threshold` and `isIntersecting` .
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Signed-off-by: Jo Steven Novaryo <steven.novaryo@gmail.com>
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>