Turn this enum into an enum class. Also m_listenerType should be OptionSet.
Pull request: https://github.com/WebKit/WebKit/pull/13603
Committed 263844@main (b4ade8e6bda5): <https://commits.webkit.org/263844@main> Reviewed commits have been landed. Closing PR #13603 and removing active labels.
<rdar://problem/109070694>