1764281 - Private Mode title is not properly updated when live language switching

Status: NEW

(Firefox :: New Tab Page, defect, P3)

Description

[Petruta Horea [:phorea], Desktop QA]

Note:
This is a follow-up of Bug #1760825

Environment:
Firefox 100 beta 4, latest Nightly 101.0a1
Win 10 64-bit, OS X 11, Ubuntu 22.04

Preconditions:
user_pref("intl.multilingual.downloadEnabled", true);
user_pref("intl.multilingual.enabled", true);
user_pref("intl.multilingual.liveReload", true);
Install languages:
about:preferences /Language - Search More Languages/Select Language to add / Add.

STR:

1. Install a Firefox locale, en-us for example (autoset region not that relevant).
2. Locate languages and install a few languages
3. Open a new Private Window and several new tabs
4. Open about:preferences / Language.
5. Switch the language to anything previously added

Actual results:
Private mode tabs title is not modified for the tabs that were already opened when the language was changed. The tab title is localized for tabs opened afterwards.

Expected results:
The localized title is modified in Private windows, just like for Normal windows.