So pretty much this is openViewOnFocus, with a couple changes.

The first difference is that we should still open the view in the newtab page, provided there is a search string. This is compatible with the current behavior for topsites since it doesn't overlap it.

The second difference is relative to private browsing, we don't open the view for top sites in PB mode, it's unclear whether we should do the same in this case, so I'm asking Verdi on Slack.

(In reply to Marco Bonardo [::mak] from comment #1)

So pretty much this is openViewOnFocus, with a couple changes.

Yeah, I think it should also depend on that mode actually being enabled. I'm not sure what the plan is there beyond the top sites experiment; are we considering enabling open-view-on-focus in 71?

Verdi clarified it should work the same in PB mode.

I was problably wrong about the overlapping though, I can't just flip the pref.
If there's a search string and the megabar is enabled, we can surely open the view.
But, if there's no search string, we should open the view only on request (like for the topsites experiment).
I can likely reuse the same hook points, just not the openViewOnFocus pref.

(In reply to Dão Gottwald [::dao] from comment #2)

Yeah, I think it should also depend on that mode actually being enabled. I'm not sure what the plan is there beyond the top sites experiment; are we considering enabling open-view-on-focus in 71?

I think openViewOnFocus will pretty much relate to the empty-string case and we'll likely flip that pref once we decide what to show in that case (top sites? something else). This depends on the experiments result.

https://hg.mozilla.org/mozilla-central/rev/d89319819e43

I reproduced this issue using Fx 71.0a1 (2019-09-05).
I can confirm this issue is fixed, I verified using Fx 74.0a1 (2020-02-04), on Windows 10 x64, Ubuntu 18.04 and macOS 10.15.
Updating the flags accordingly.