Odd, that's what I use:

# cat /usr/local/etc/dnsmasq.conf address=/dev/127.0.0.1

# cat /etc/resolver/dev nameserver 127.0.0.1

Instead of your choice of foobar.

Doesn't work offline. Your conf looks like the standard dnsmasq conf anyway, so maybe there's one other flag or configuration that you figured out?

I've searched high and low after reading your reply, trying for an hour to jog my memory of how I got that to work.

Well, I found it — quite a few entries in /etc/hosts, made at 02:30 AM, together with unflattering comments about the parents of those responsible for Yosemites new DNS subsystem...

So sorry for getting your hopes up! I have no idea how I could have misremembered all that so badly.

the difference I see is that you are missing a period before "dev" in your dnsmasq.conf

I don't know how to configure dnsmasq at all, so that may not be a problem.

I ran into the same problem with Yosemite when offline in a plane this weekend. I'm using the same setup as you except I have .dev instead of just dev.