We need to enable requestIdleCallback, as in bug #260369. Ryosuke has left us this hint: """ You need to implement these functions: RunLoopObserver::schedule, RunLoopObserver::invalidate, and RunLoopObserver::isScheduled(): https://github.com/WebKit/WebKit/blob/main/Source/WebCore/platform/RunLoopObserver.cpp """ Unfortunately, looking at RunLoopObserverCF, I can't think of any way to map this to GMainContext, so it's probably not possible. We shouldn't try to modify GMainContext unless there are no other options. This requires further investigation. -------------------------------------------- We should also think about the problem I describe here: https://bugs.webkit.org/show_bug.cgi?id=164193#c18, i.e. we need to make sure web content cannot perform a denial of service that would prevent WebKit from running WebKit's own callbacks.