Bug 1476309 - use RemoteSettings for Tippy Top

[rlr]

@ncloudioj to test it out, you need to change the prefs for RS. I just run the following in the browser console:

const SERVER_STAGE = "https://settings.stage.mozaws.net/v1";
const HASH_STAGE = "DB:74:CE:58:E4:F9:D0:9E:E0:42:36:BE:6C:C5:C4:F6:6A:E7:74:7D:C0:21:42:7A:03:BC:2F:57:0C:8B:9B:90";
Services.prefs.setCharPref("services.settings.server", SERVER_STAGE);
Services.prefs.setCharPref("security.content.signature.root_hash", HASH_STAGE);

[ncloudioj]

LGTM!

@leplatrem, could you also take a look at this please (the client side change of bug 1437671)?

The key change of this patch is that we use RemoteSettings to replace the old JSON Tippytop manifest (manually sync'd to its origin on S3).

Note that since the Tippytop functionality is not sensitive to the data latency (add/update/delete) in Activity Stream, we completely rely on the default syncing strategy of RS. We've also removed the memory cache for the Tippytop manifest, and implemented the lookup directly on top of RemoteSettings.get(). That at least considerably simplified the code : ).

Would love to hear your thoughts on those changes.

[leplatrem]

It looks good ! Nice refactor indeed :)

[leplatrem]

nitpick: could also be shortened as this.tippyTop.get({filters: {domain}});

[leplatrem]

nitpick: since the rest of the function is useless when site is null, maybe:

if (!site) {
  return;
}

[leplatrem]

An alternative to this would be to store records in the local db:

const collection = await RemoteSettings("tippytop").openCollection();
await collection.create({
  domain,
  image_url: `${url}/icon.png`
});

But this may require to setup IndexedDB in your tests suite, which may not be obvious