[imajoredinecon]

There might be more to the privacy characteristics of an API like this than meets the eye. For instance, if a user grants camera permissions scoped to http://insecure.website in order to scan a QR code and get it detected, it might be surprising to the user that on-path attackers would be able to see the user’s camera snaps. Making the API work in a degraded mode in insecure contexts (e.g. by disabling particularly privacy-sensitive data sources) might be a plausible alternative, but at this point it’s arguably cleaner and less risky to just make the interface HTTPS-only in order to avoid making developers and users reason through these nuances.

[xg15]

I don't get it. The privacy risk in there is from getUserMedia(), which is already (correctly) https-only. There is no privacy risk coming from the barcode API itself.