Is it possible for an extension detect when loading a web site times out?

I’m trying to detect the initial “connection timed out” error. I’ve gotten a webRequest onErrorOccurred listener working for problems after a page loads, but that doesn’t seem to trigger when the initial page is retrieved. Is this possible?

Welp, now it’s working. No idea why but it just started working the billionth time I reloaded my local extension…