ChromeOS version: 69
ChromeOS device model: Eve
Case#: 16993445

Description:
ARC++ apps ignore proxy auth requests if the login times out while user is in a ARC++ app. If the user is in a Chrome browser session, they are properly prompted for credentials.

Steps to reproduce: 
1. whitelist all Chrome OS SSL whitelist hosts so they do not request proxy auth.
2. Place device behind a authenticated proxy.
3. Observe, when prompted to auth in browser session, the user can enter credentials and gain access.
4. Observe, when prompted to auth in a ARC++ app, the app ignores the 401 auth required response and fails the connection.

Current Behavior / Reproduction: 
ARC++ apps do not respond to 401 requests to re-authenticate

Expected Behavior: 
User should be prompted to re-enter credentials for proxy.

Drive link to logs: 
https://drive.google.com/drive/folders/1Ki-qvHqrKTV4SaEWqCY-J5hcPN8_K9Yu?usp=sharing