[Reader IA] Fix top navigation bar disappearing when system has low-memory

[thomashorta]

Fixes #20105

A couple of things were done to fix this issue:

• Try to wait for a non-null top app bar state in functions that REQUIRE an existing top app bar to work
• Properly save and restore top bar state using the Reader Fragment Saved Instance State Bundle

---

To Test:

1. Enable the don't keep activities option.
2. Install and log into Jetpack
3. Go to the Reader
4. Go to the Subscriptions feed
5. Open a single post in the reader
6. Tap back
7. Verify that the top bar is still there in the correct state

Also, try doing that in other feeds, including selected blog/tag filters, to confirm the top bar does not disappear and saves the correct state.

---

Regression Notes

1. Potential unintended areas of impact

   • Wrong top bar state being shown at any given time.

2. What I did to test those areas of impact (or what existing automated tests I relied on)

   • Manual changes

3. What automated tests I added (or what prevented me from doing so)

   • None yet. Unit tests should be added in a future PR to cover the fixed scenarios.

---

PR Submission Checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

---

UI Changes Testing Checklist:

• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• Talkback.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• Large and small screen sizes. (Tablet and smaller phones)
• Multi-tasking: Split screen and Pop-up view. (Android 10 or higher)

[dangermattic]

	1 Warning
⚠️	PR is not assigned to a milestone.

Generated by 🚫 Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr20114-777633f
	Commit	777633f
	Direct Download	jetpack-prototype-build-pr20114-777633f.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr20114-777633f
	Commit	777633f
	Direct Download	wordpress-prototype-build-pr20114-777633f.apk

Note: Google Login is not supported on these builds.

[peril-wordpress-mobile]

	Warnings
⚠️	PR is not assigned to a milestone.

Generated by 🚫 dangerJS

[codecov]

Codecov Report

Attention: 45 lines in your changes are missing coverage. Please review.

Comparison is base (f37f1ec) 40.48% compared to head (777633f) 40.47%.
Report is 210 commits behind head on feature/reader-ia.

Files	Patch %	Lines
...ss/android/ui/reader/viewmodels/ReaderViewModel.kt	13.46%	42 Missing and 3 partials ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##           feature/reader-ia   #20114      +/-   ##
=====================================================
- Coverage              40.48%   40.47%   -0.01%     
=====================================================
  Files                   1447     1447              
  Lines                  66788    66812      +24     
  Branches               11030    11030              
=====================================================
+ Hits                   27036    27045       +9     
- Misses                 37268    37279      +11     
- Partials                2484     2488       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[develric]

Code LGTM @thomashorta , also I was able to replicate consistently on a pixel 4 emulator, the VM gets deallocated and with the PR patch when it is reinitialized restores the state correctly from the saved state 👍

I'm approving this one 🙇