Simplify ExpansionBehavior to avoid using getters/setters
Pull request: https://github.com/WebKit/WebKit/pull/947
Committed r294758 (250926@main): <https://commits.webkit.org/250926@main> Reviewed commits have been landed. Closing PR #947 and removing active labels.
<rdar://problem/93852055>
*** Bug 240822 has been marked as a duplicate of this bug. ***