Chrome Version: 65.0.3325.209
Chrome OS Version: 10323.67.0

Steps To Reproduce:
1) Force install an extension like Weather Buddy - https://chrome.google.com/webstore/detail/weather-buddy/bpbhcboindgomhjpohahlaoonfinnmkf to a public session.
2) observe, the manifest does not request *ANY* permissions. Manifest can be viewed at https://cws-check.appspot.com/?appid=bpbhcboindgomhjpohahlaoonfinnmkf
3) When user in public session clicks extension icon, they are prompted by Chrome "Weather Buddy" has requested additional permissions. - It could - Read and change all your data on the current website when invoked."
4) Observe, the app is fully functional (enter area code, get weather) even while permissions prompt is up. If user denies permission, app remains fully functional.
5) Observe, if user chooses to allow permission and then opens devtools and runs:

chrome.permissions.getAll(function logPerms(perms) { console.log(perms); });

zero permissions are current allowed for the extension in spite of the allow.

Expected Result:
Because the extension does not request any permissions or optional permissions, user should not be prompted to grant permissions.

Actual Result:
User is prompted to grant permissions, allow or deny has no affect on operation of extension.

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)
10/10

What is the impact to the user, and is there a workaround? If so, what is
it?
Confusing public session behavior, user may be concerned the extension or owner of PS device is attempting closer monitoring of activity than they actually are.

Please provide any additional information below. Attach a screen shot or
log if possible.
Issue seems to repro with ANY extension that uses a popup. I chose Weather Buddy since it does not request any permissions at all but issue also reproduces with:
kdpaldfdmbhojkkaebckeknoempakldh - Drink Water
gbhbpcekmnphpkpkepfailabmnbfcdjb - Chrome Device Info (my extension)

Seems likely it's related to  crbug.com/717945  which implemented forced user permissions prompt for force-installed extensions with ActiveTab permission.