There are some feature guards that are incorrect in WPE code.
Created attachment 355301 [details] Patch
Comment on attachment 355301 [details] Patch Patch LGTM (informally reviewing).
Comment on attachment 355301 [details] Patch Clearing flags on attachment: 355301 Committed r238397: <https://trac.webkit.org/changeset/238397>
All reviewed patches have been landed. Closing bug.