Fix FXiOS-12300 [Tab Optimization] Only persist tab data after tabs have been removed

[Cramsden]

📜 Tickets

Jira ticket
Github issue
Jira ticket
Github issue

💡 Description

Clean up remove tab logic so we are only doing the necessary tab persistence. Everywhere in the tab manager code we are persisting data more times than we need to. We should not need to re-select the tab and persist tab session data for each tab we remove.

This update:

1. Save backup tab data for undo tab deletion (only available on iPad)
2. Persists tab session data for currently selected tab to maintain scroll position updates
3. Loop through current version tabs and delete them
4. If you are in private mode update selected tab to current recently selected normal tab
5. If you are not in private mode create a new tab and select it

There is no need to commit changes after this because select tab preserves tabs

With 200 tabs this greatly increases the tab performance.

TabManager.removeAllTabs
Before: 5.15 s 37.7%
After: 41.00 ms  3.4%

🎥 Demos

Before	After

Demo

📝 Checklist

• I filled in the ticket numbers and a description of my work
• I updated the PR name to follow our PR naming guidelines
• I ensured unit tests pass and wrote tests for new code
• If working on UI, I checked and implemented accessibility (Dynamic Text and VoiceOver)
• If adding telemetry, I read the data stewardship requirements and will request a data review
• If adding or modifying strings, I read the guidelines and will request a string review from l10n
• If needed, I updated documentation and added comments to complex code

[mattreaganmozilla]

@Cramsden I haven't had a chance to take a close look, is this effectively the same basic approach as #26782? FYI I saw a weird index-related crash when testing my optimization, which I was concerned about. It was intermittent though and I still haven't had time to verify whether it was related to the optimization changes.

[lmarceau]

FYI just in case, there's a contributor PR opened for that same area of the code.

[mobiletest-ci-bot]

	Messages
📖	Project coverage: 37.83%

💪 Quality guardian

1 tests files modified. You're a champion of test coverage! 🚀

🧹 Tidy commit

Just 2 file(s) touched. Thanks for keeping it clean and review-friendly!

💬 Description craftsman

Great PR description! Reviewers salute you 🫡

✅ Per-file coverage

All changed files meet the threshold of 35.0%.

Client.app: Coverage: 37.24

File	Coverage
TabManagerImplementation.swift	55.35%	✅

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