ThreadedCompositor::setNeedsDisplay() is always called from the main thread and schedules a task to the compositing thread to schedule an immediate update. But RunLoop::Timer is thread-safe so we don't really need to schedule a task to the update the timer in the compositing thread, we can do that directly in the main thread. And that's exactly what scheduleDisplayImmediately() do, so we can use that instead of setNeedsDisplay().
Created attachment 280802 [details]
Committed r201859: <http://trac.webkit.org/changeset/201859>