OK, that sounds scary. It happened again. So, I looked online and it said that one thing that could cause it would be a peripheral. I was to unplug any peripherals, shut the mac down and reboot, leaving the peripheral unplugged. If the error message didn't happen again, it's the peripheral causing it. So far, after doing that, it hasn't happened again. Maybe tomorrow I will replug in my Logitech speaker and see if it happens again. If so, I know what the culprit is.
Thanks for responding.
WebKit was indeed running, however that dump is for a kernel panic. Something happened deep in the kernel that should never have happened, apparently with the process scheduler.
Broadly speaking, no user space program should ever be able to panic a kernel. The fact that it did uncovered a bug in the kernel that only Apple can fix.
