They were introduced for FontCachePurgePreventer. But it's not a thing anymore.
<rdar://problem/35022452>
Created attachment 323990 [details] Patch
Comment on attachment 323990 [details] Patch Attachment 323990 [details] did not pass ios-sim-ews (ios-simulator-wk2): Output: http://webkit-queues.webkit.org/results/4879417 New failing tests: webrtc/video-replace-muted-track.html
Created attachment 323998 [details] Archive of layout-test-results from ews122 for ios-simulator-wk2 The attached test failures were seen while running run-webkit-tests on the ios-sim-ews. Bot: ews122 Port: ios-simulator-wk2 Platform: Mac OS X 10.12.6
Comment on attachment 323990 [details] Patch Clearing flags on attachment: 323990 Committed r223549: <https://trac.webkit.org/changeset/223549>
All reviewed patches have been landed. Closing bug.