Description

A small number of Zero providers restrict the wiki languages for which data is zero-rated. Going from a zero-rated language to a non-zero-rated language should trigger a state change event that warns the user traffic is no longer zero-rated, but currently no such event is triggered.

Interestingly, a state change event does occur when going in the other direction, from a non-zero-rated language to a zero-rated language.

See also semi-related bug T126997: [Bug] Switching the Wikipedia language while Zero is enabled does not update the nav menu zero message.

Steps to reproduce

1. Enable zero-rating on a provider with only some languages whitelisted
2. Obtain Wikipedia Zero state in the app
3. Change the Wikipedia Language to a non-zero-rated language and continue browsing

Expected results

A state change event is triggered, notifying the user that Wikipedia Zero is no longer active.

Actual results

No such state change event is triggered, and the Wikipedia Zero chrome remains in place.

Environments observed

App version: dev
Android OS versions: M
Device model: 6P
Device language: English