PSA: Cronet is deprecating Android Jelly Bean support

[Stefano Duo]

Hi net-dev,

Cronet is deprecating Android Jelly Bean (API level 16-18) support. Going forward, the minimum supported version will be Android KitKat (API level 19).

https://crbug.com/1271882 has been created to keep track of the process and to answer any questions or concerns.

If you maintain Chromium code that is still supporting Jelly Bean only because of Cronet, file a bug blocked on https://crbug.com/1271882.