Safari iOS doesn't support api.WorkerGlobalScope.languagechange_event

[ddbeck]

Summary

This was probably never supported.

Test results and supporting details

This is very difficult to test because it requires changing the system language settings, which I can't do in BrowserStack. And I don't have a device that I can directly test with. But I learned a few things:

• In a window, languagechange fires in contemporary macOS Safari.
• In a worker, languagechange does not fire in macOS Safari and onlanguagechange doesn't appear to be real (e.g., you can assign arbitrary types to it, unlike the window equivalent).
• Following the blames shows this data was originally migrated from the wiki. Add compat data for WorkerGlobalScope (Worker API) #982
• Searching webkit/webkit shows evidence of the window exposure, like tests, but I couldn't find anything even hinting at worker exposure.

Taken together, I'm rather certain that Safari doesn't actually support this and it's spurious data from the wiki days.

Related issues

Discovered reviewing web-platform-dx/web-features#1931

[caugner]

Reasoning is plausible.