Add option to Undo when user presses "Erase"

[mikailmikhail]

Posting an issue for triage per @oliviabrown9 recommendation on #992.

It may be worth considering adding the option to Undo following the Erase option. Possible that a user hits the Erase button by mistake when browsing, trashing their browsing session.

This could be as simple as a pattern similar to undoing tab closure in Firefox:

[oliviabrown9]

This is an interesting idea. The major issue I have with it is that we would, in fact, have to store some of the user's browsing history in order to have this option work, which would contradict the whole message of "Your browsing history has been erased." I fear that this could cause users to trust Focus less. Of course, we would be able to actually erase their history once they neglected to to "undo," but there are so many circumstances I could see arising that make me wary. For example, what if someone erased their session and handed their phone to someone else, who would then have the option to "undo" the erase, potentially revealing a past session that a user wouldn't want seen.
@brampitoyo what are your UX thoughts on this?

[brampitoyo]

@oliviabrown9 Thanks for bringing up your privacy concerns. They’re valid!

To help minimise any risk, we need to make sure that:

1. The notification doesn’t appear for too long, and disappear automatically even when not interacted with. I think the current notification lasts for ~3 seconds. I agree with this approach, and we shouldn’t make it shows up any longer.
2. When the banner is gone, there’s no other way to recover history. This means that, after 3 seconds, your information is truly gone. To thwart against a malicious adversary, then, the user will only need to keep the phone in their hands for as long as the notification shows up.

Does this help assuage some of your concerns? Do you have some other that we’re not aware of?

[bbinto]

Similar feature request for Android mozilla-mobile/focus-android#467