We use a different priority for the main thread shared timer to match GDK_PRIORITY_REDRAW, but that doesn't make much sense nowadays because there aren't GDK events in the web process anymore. But it still makes sense to use different priorities depending on the kind of source.
Created attachment 306177 [details]
Created attachment 306479 [details]
Committed r215088: <http://trac.webkit.org/changeset/215088>
Regression in bug #171218