DidFirstLayerFlush IPC can be head-of-line-blocked and delay first paint by 200+ ms on process sawp
Created attachment 396571 [details]
Created attachment 396574 [details]
Comment on attachment 396574 [details]
Seems like a great way to fix this particular issue (even without adding a general priority mechanism to task scheduling). I'll wait for Tim and Simon to tell me why I'm wrong :P.
Created attachment 396576 [details]
Created attachment 396584 [details]
Patch for landing
Committed r260158: <https://trac.webkit.org/changeset/260158>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 396584 [details].
Note that I have a patch in https://bugs.webkit.org/show_bug.cgi?id=208413 for general RunLoop priorities if we want to do something more generic.