Layer flush throttling also stops style recalcs and layouts. Layouts schedule layer flushes. Especially on a slow network we can in principle end up in situation where layer flush timer fires but there is no flush scheduled and so nothing happens. However there is a pending style recalc or layout that would actually schedule a flush (in practice various things force style recalcs and this doesn't occur commonly).
To avoid this we should flush unconditionally when the flush timer fires. This performs any pending style recalc and layout too. If there is nothing to do the flush will be cheap.
Created attachment 355275 [details]
Comment on attachment 355275 [details]
Clearing flags on attachment: 355275
Committed r238394: <https://trac.webkit.org/changeset/238394>
All reviewed patches have been landed. Closing bug.