[Bug]Backgrounded custom tab is lost when opening Fenix

[AndiAJ]

Prerequisites

Gmail, Reddit, Twitter, Cnet app's are opened.
Fenix is set as the default browser app.

Steps to reproduce

1. Open a custom tab using Reddit.
2. Exit to the home screen and open Fenix.
3. Open a custom tab using Gmail
4. Exit to the home screen and open Fenix
5. Open a custom tab using Cnet
6. Exit to the home screen and open Fenix
7. Open a custom tab using Twitter
8. Exit to the home screen and open Fenix

Expected behavior

The custom tabs shouldn't be lost. Fenix browsing session should be opened separately, not in each of the native apps'.

Actual behavior

The custom tab is lost and a new Fenix browsing session seems to be opened in the native app's.

Device information

• Android device:
  • Google Pixel 3a (Android 9)
  • Huawei Mate 20 Lite (Android 8.1.0)
  • Samsung Galaxy S7 (Android 7)
  • OnePlus A3 (Android 6.0.1)
  • LG Nexus 4 (Android 5.1.1)

• Fenix version: Nightly Build #20080616 from 01/08

Notes

❗ Not reproducible on yesterday's Nightly Build #20070606 from 1/7
Reproducible with Custom tabs in Private Mode.

► Video

┆Issue is synchronized with this Jira Task

[sv-ohorvath]

Also reproducing on Beta 4.0-beta 1

[liuche]

We should get this fixed by end of week to get uplifted to Beta Migration in a subsequent build, but we won't block 4.0 release/first beta migration build on this.

[liuche]

@baron-severin if you could take a look

[liuche]

Actually, jon mentioned this might be a dupe of #5041, so QA, could you verify and see if it is already fixed?

[jonalmeida]

Actually, jon mentioned this might be a dupe of #5041, so QA, could you verify and see if it is already fixed?

Sorry for the confusion, it's definitely NOT fixed according to that bug, but it's just duplicate issue so I mentioned it to avoid duplicate tracking. Feel free to close either one. #5041 has some more technical details and potential fixes in r-b that Fenix might be able to use.

[severinrudie]

@liuche @jonalmeida I believe this is actually a different (although quite possibly related) bug. There are two broken flows in the above report/gif, and neither is quite the same as #5041.

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Open third party app -> open custom tab -> tap home button -> tap Fenix shortcut
EXPECTED: opens Fenix normal session
ACTUAL: opens to third party custom tab (or blank home, when combined with the below flow)

Reproducible for me on Release v3.2.1, but not reproducible on Nightly 200222 18:21 (Build #20531827)

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Open third party app -> open custom tab -> tap home button -> open recently used list -> select third party app
EXPECTED: custom tab
ACTUAL: appears as third party app on recently used list, but shows Fenix home

Not reproducible for me on Release 3.2.1 or Nightly 200222 18:21 (Build #20531827)

[AndiAJ]

Hi, verified as fixed, on the latest Nightly Build #20560606 from 02/25 using the following devices:

• Google Pixel 3a (Android 9)
• Huawei Mate 20 Lite (Android 8.1.0)
• Samsung Galaxy S7 (Android 7)
• OnePlus A3 (Android 6.0.1)

► Video