Add SYNC-3478 [v109] Poll for missing send tabs on interval

[tarikeshaq]

On desktop and android, we poll for missed send tabs occasionally. For iOS, we only poll for send tabs when we receive a notification (and even then, we only poll for exactly one tab). This PR changes it so we poll for missing commands whenever we sync the clients collection.

Happy to take any feedback here. Creating the PR as a starting point. Keeping as a draft as I do more testing on a physical device

Questions:

What's the user experience:

• I'll upload a small gif recording, but its:
  • Once the browser detects that there are missing tabs, it would open and switch to them

Would this increase load to the FxA servers

• Yes, but now we are mimicking Firefox Desktop, so the load on FxA shouldn't be dramatically impacted
  • We will poll once a day on a scheduled sync
  • We will poll on sync now
  • We will poll when we detect that our FxA push endpoint has expired

Now that we poll, what happens to users who didn't get their tabs in the past?

• Each send tab has a TTL of 30 days. Users will get all the tabs they sent and lost in past 30 days, but they won't get anymore.
• That said, I'm happy to make the first poll a noop, so we silently drop tabs that could have been sent before this so that we don't surprise users.

[tarikeshaq]

Going to add a test for pollCommands but this should be ready for review - I'll also do some testing on a physical device, since this PR also changes the push notification handling

[OrlaM]

A small nit if you feel like changing it, otherwise LGTM.

[tarikeshaq]

Thanks a ton for the review @OrlaM 🙏 I added one more commit after doing testing on my physical device

Unfortunately couldn't find any testing infra for BrowserProfile so testing pollCommands properly seemed more trouble than its worth

If it looks good, I would love to see this land (I don't have permission to land PRs 😞)

[tarikeshaq]

I'm mildly surprised send tab even works in prod correctly. I had to add this because my device couldn't receive send tabs properly, and after debugging I found that the culprit is that the NotificationService on my device is running a background thread when receiving messages

This causes it to crash and deliver a default notification instead of the actual tab

I'm assuming in production builds (and in beta I tested to make sure) the notification service runs on the main thread somehow? regardless dispatching this onto the main thread fixed local push notification for me on my iPhone

[tarikeshaq]

Let’s hold off on merging this while I confirm one more thing! Tapping on a push notification while the app is backgrounded is not launching the tab - I’ll flag once I figure out what’s going there

[OrlaM]

Might be worth checking if that actually works on main. We made the switch to use SceneDelegates recently which has caused a few deeplinking bugs to pop up, so might not be caused by your PR.

[tarikeshaq]

Rebased on main the problem fixed itself! This should be good to land, with an enhancement coming soon in the next application-services release. Currently, if we get a push notification and we poll soon after, it's possible that the poll would reopen the same tab again

This is possible if the account manager didn't refresh its state before the next poll, since the notification service has its own instance of the account manager.

I'll have a PR next week with a new AS release to make it impossible