When we were working on Bug 1257565, since we had no idea how to switch the blocklist service to async, our first approach was to generate JSON files on disk and load them the same way as the current XML file. Since then, Gijs has accomplished a ton of work to switch the blocklist service methods to async, and demostrated that using the RemoteSettings API directly was a relevant approach. We can now get rid of those JSON files, they are and will remain completely useless.

Don't we use the JSON dumps to do the initial creation of the database for new profiles?

The JSON dumps we use for the initial creation of the database are packaged in the release in `services/settings/dumps` and loaded from resource:// The JSON files in the profile were the result of some «work-in-progress» for Bug 1257565. Our initial plan was to write those files on disk after server synchronization, send a reload-from-disk message and read them synchronously in the blocklist service. The two first steps were landed in Bug 1257556 if I recall correctly. The third never happened as you can in the pending patches in Bug 1257565 Anyway, since we now know that we can use the `async RemoteSettings().get()` in the blocklist service, these JSON files can be cleaned from profiles. Also we now have `RemoteSettings("..").on("sync", {})` therefore we don't need to emit a message to wake up the blocklist service.

Comment on attachment 8986140 [details] Bug 1469525 - Remove blocklist clients files from profile https://reviewboard.mozilla.org/r/251586/#review257866

Pushed by mleplatre@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/ace07e18cb34 Remove blocklist clients files from profile r=Gijs