In Developer mode, with adb debugging switched on in the Android Developer options, if we connect to Android via adb in the Chrome OS shell
sudo su -
adb connect 100.115.92.2
We can then switch on mock locations via adbadb shell settings put secure mock_location 1
If a suitable fake location Android app (e.g. https://play.google.com/store/apps/details?id=com.lexa.fakegps) is installed on the device, this can be set as the default mock locations appadb shell appops set com.lexa.fakegps android:mock_location allowTo set a different app as the mock locations app, change the package name/App ID (com.lexa.fakegps in the example above) to the appropriate package name (as shown on the app's Play Store URL).
After setting Fake GPS as the mock locations app, I was able to select my mock location in Fake GPS and e.g. Maps in Opera would successfully show the mock location, rather than my current location. I haven't really tested in many other apps at this time.
I understand that some Android apps may specifically check if mock locations are being used. For those apps, I imagine further steps would probably be required, such as perhaps installing (possibly a different app such as GPS JoyStick) as a system app. This, however, would require remaking the Android rootfs container as a R/W image. If this is required, the rooting script can be run, which, as part of the rooting process, replaces the Android read-only rootfs with a R/W copy.
