It should be possible to simplify IPC::Attachment to the point of just using UnixFileDescriptor in its place, on relevant platforms.
Pull request: https://github.com/WebKit/WebKit/pull/4831
<rdar://problem/100850821>
Committed 255620@main (137c50abcab7): <https://commits.webkit.org/255620@main> Reviewed commits have been landed. Closing PR #4831 and removing active labels.