This is a follow-up to #425.
“Tracking protection” is a service-based part of SafeBrowsing that, like Google Safebrowsing (the original reason for it), doesn’t work without an API key.
We should treat Tracking Protection (i.e. “Disconnect operated by Mozilla”) part of a package with Google SafeBrowsing because these are part of Mozilla-instrumented/supplied services for Firefox and Firefox only.
MOZ_SAFEBROWSING should therefore guard all code comprising Google Safebrowsing and Tracking Protection, making sure neither of these are built when SafeBrowsing isn’t built.
As a potential follow-up down the road this issue will also make it easier to completely remove this from our tree if no applications building on UXP have any interest in funding/operating this service.