The enums already use the new serialization format and are defined in WebExtensionStorage.serialization.in
Pull request: https://github.com/WebKit/WebKit/pull/23516
Committed 273825@main (5495e9f832d3): <https://commits.webkit.org/273825@main> Reviewed commits have been landed. Closing PR #23516 and removing active labels.
<rdar://problem/122010731>