Bugzilla

This bug covers adding the advertiser name and tile ID to the `topsites.impression` and `topsites.click` events for sponsored tiles.

I'm marking it moco-confidential for now, because it's sensitive data that depends on the outcome of the [data review](https://wiki.mozilla.org/Data_Collection#Step_3:_Sensitive_Data_Collection_Review_Process) thread that :chutten started.

As part of this, I think we'll want to add:

* `advertiser` and `tile_id` keys to the [Glean events](https://searchfox.org/mozilla-central/rev/736eb58cd30da3afc0310b58232a1e4d0dcc86a4/browser/components/newtab/metrics.yaml#251,282) for impressions and clicks.
* Instrumentation to `TelemetryFeed.jsm` that records these keys for [sponsored tiles](https://searchfox.org/mozilla-central/rev/736eb58cd30da3afc0310b58232a1e4d0dcc86a4/browser/components/newtab/lib/TelemetryFeed.jsm#876-879,889-892).

This bug covers adding the advertiser name and tile ID to the `topsites.impression` and `topsites.click` events for sponsored tiles.

I'm marking it moco-confidential for now, because it's sensitive data that depends on the outcome of the [data review](https://wiki.mozilla.org/Data_Collection#Step_3:_Sensitive_Data_Collection_Review_Process) thread that :chutten started.

As part of this, I think we'll want to add:

* `advertiser` and `tile_id` keys to the [Glean events](https://searchfox.org/mozilla-central/rev/736eb58cd30da3afc0310b58232a1e4d0dcc86a4/browser/components/newtab/metrics.yaml#251,282) for impressions and clicks.
* Instrumentation to `TelemetryFeed.jsm` that records these keys for [sponsored tiles](https://searchfox.org/mozilla-central/rev/736eb58cd30da3afc0310b58232a1e4d0dcc86a4/browser/components/newtab/lib/TelemetryFeed.jsm#876-879,889-892).
* Tests covering the new instrumentation ☺️

Here are some things I found really helpful when adding instrumentation for organic tiles in bug 1820707:

* The [metric types reference](https://mozilla.github.io/glean/book/reference/metrics/index.html) from the Glean book.
* Other metrics in the `metrics.yaml` file, for inspiration.
* Bug 1766887, which initially added the `newtab` ping and metrics.
* Some discussion in the patch for bug 1688698 about the different telemetry instrumentation for Pocket ("Discovery Stream") sponsored vs. non-Pocket sponsored and organic tiles.
* The [Data Collection page on the Mozilla wiki](https://wiki.mozilla.org/Data_Collection) with an explanation of the data review process, and links to the forms.
* Bug 1733443, comment 3 for an explanation of how the potentially sensitive data review (step 3) is handled.

When I'm hacking on New Tab locally, I use:

* `./mach npm run testmc:unit --prefix=browser/components/newtab` to run the Node-based unit tests for New Tab.
* `./mach npm run bundle --prefix=browser/components/newtab` to rebuild the bundle—only needed once you're ready to push your changes.

Running the Node tests can take quite a while, and I didn't find (after like a minute; I didn't look very hard 😅) a way to make Karma run just a subset. But I found that editing [this line](https://searchfox.org/mozilla-central/rev/736eb58cd30da3afc0310b58232a1e4d0dcc86a4/browser/components/newtab/test/unit/unit-entry.js#31) with just the test files I wanted to run, to something like this:

```js
const files = req.keys().filter(file => file.endsWith("/TopSites.test.jsx"));
```

...worked perfectly, so I didn't poke further.

I had great results with using `./mach try auto` to run the tests on automation, too.

We can't use [artifact builds](https://firefox-source-docs.mozilla.org/contributing/build/artifact_builds.html) when adding / changing Glean metrics yet, but I think we'll be able to again once bug 1820241 is fixed! 🎊