FNX-14508 ⁃ For #11903: Fix private custom tabs

[NotWoods]

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

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[codecov-commenter]

Codecov Report

Merging #13327 into master will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master   #13327      +/-   ##
============================================
- Coverage     28.48%   28.48%   -0.01%     
- Complexity     1046     1047       +1     
============================================
  Files           420      420              
  Lines         16968    16970       +2     
  Branches       2200     2202       +2     
============================================
  Hits           4834     4834              
- Misses        11786    11788       +2     
  Partials        348      348              

Impacted Files	Coverage Δ	Complexity Δ
...n/java/org/mozilla/fenix/IntentReceiverActivity.kt	74.35% <100.00%> (+1.38%)	7.00 <5.00> (+1.00)
...mponents/searchengine/FenixSearchEngineProvider.kt	62.16% <0.00%> (-1.81%)	13.00% <0.00%> (ø%)

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[ekager]

So AFAICT this getIntentProcessors will also process externalAppIntentProcessors and others. Before even though it wasn't working (lol) it was attempting to just add this extra on the custom tab and intent processors. Will there be any bad side effects from adding this extra to other intent entry points?

[NotWoods]

There shouldn't be side effects when we add extra intents. If we want to be super safe we can set the boolean on both this.intent (before) and the home activity intent (now).

[ekager]

Sorry that was a confusing comment. I meant as an example - now the TWA/PWA externalAppIntentProcessors will also be attaching PRIVATE_BROWSING_MODE, right? Does that mean PWAs will also be attempting to present / be in PBM?

[NotWoods]

Honestly we wanted it to work that way in the first place, so if they do present in PBM that fixes another bug :)

We can do another pass in the future to re-evaulate what data is getting passed in intents like this.