Set fall back or default geolocation in Google Chrome?

No luck on the official side.

On the not so official side, however, there is a "geolocation" object in the configuration file (assuming you are on OSX, otherwise you'll have to look for this file)

~/Library/Application Support/Google/Chrome/Local State

that contains the server address

https://www.google.com/loc/json

Maybe (and I emphasize maybe) if you change this address to something you can control, you can feed Chrome with the location you want.

I don't have the opportunity at the moment to test it, but I will in a few hours and will report back my results.

In the meanwhile, if you want to give it a shot...

EDIT: I thought I would have had a chance in a few hours... turns out I didn't and I won't for the day, sorry...