*edit: I'd genuinely be surprised if google made it that easy to not send anything back to them. Additionally, I'd be genuinely surprised if FF made it that simple to avoid sending things back to Mozilla.
(You can easily check this with an app like Little Snitch, look for the browser connecting to IPs 8.8.8.8 and 8.8.4.4)
I also just noticed that Little Snitch actually does NOT log the dns requests. Maybe this is caused by Chromium using ipv6 to access google-public-dns-a.google.com ?
Anyway, I then installed Vallum (1) and with this app, in the log i see many of these requests: https://i.imgur.com/lUR3Fd7.png
I mean if we're going to go to this level of paranoid; then we might as well look at attacks on Firefox (which have been suspected to be used by the NSA against Tor Browser).
It's less about being covert, and more about having multiple settings to send different types of data back.