FxA Auto Sign-in

[vesta0]

Why/User Benefit/User Problem

As a user I want the option for Fenix to automatically sign me in my Firefox account if I am currently signed in FxA on Fennec on the same device.

Acceptance Criteria

-I see a prompt during Fenix onboarding, asking me if I want to sign into my Firefox Account (if I am already signed into FxA on Fennec on my device)
-I can tap on the prompt, and be automatically signed into FxA
-Once signed in, I will be taken to the Sync page.

What / Requirements

-UX Designs ==> https://mozilla.invisionapp.com/share/XBRNF6MJVUY
Application Services dependency (Verify the as PR for session token migration works with the a-c PR for account state machine, review, and merge)

┆Issue is synchronized with this Jira Task

[apbitner]

Onboarding screens have been updated to give the user the option to stay signed in, or to sign out - https://mozilla.invisionapp.com/share/XBRNF6MJVUY

[vesta0]

Thank you so much @apbitner for the quick turnaround!

[apbitner]

No problem. Updated again this morning with minor copy edits from legal.

[boek]

This is blocked on A-S and Fennec 67

[vesta0]

@apbitner do you think "stay signed in" implies that the user has already been signed in (and had some data synced) prior to making a selection? If so we may want to change the wording to indicate that nothing is synced until they make an informed decision. Let me know what you think :)

@grigoryk FYI ^^

[lobontiumira]

This is not merged yet.
I've tested on the latest Nightly build 190731 (#12120612) with Google Pixel 3 (Android 9), and Sony Xperia Z5 Premium (Android 7.1.1). The onboarding is not updated yet, and I am signed in Fennec on the same device.