If you could return valid internal DNS entries for these domains, and serve up a 204 to the right requests, you should be able to stay online.
You need to ensure you don't do it for every possible domain - I believe Chrome also tests random non-existent domains too, to ensure it gets back the expected error.
I have a "captive" or "promiscuous" dns server (it responds with its own IP for all requests) for my esp projects so this info is exactly what I need. Thanks a lot!