[tor-bugs] #31563 [Applications/Tor Browser]: Urlbar search icons disappear after browser restart

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#31563: Urlbar search icons disappear after browser restart
-------------------------------------------------+-------------------------
 Reporter:  acat                                 |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  ff68-esr, TorBrowserTeam201908R,     |  Actual Points:
  tbb-9.0-must-alpha                             |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------
Changes (by acat):

 * keywords:  ff68-esr, TorBrowserTeam201908, tbb-9.0-must-alpha =>
     ff68-esr, TorBrowserTeam201908R, tbb-9.0-must-alpha
 * status:  new => needs_review


Comment:

 There seems to be two different paths for loading search engines: from
 cache and from scratch. Initially they are loaded from scratch, and this
 seems to ignore `extensions.enabledScopes`, so the search extensions are
 installed and that's why it works on first time. After restart, engines
 are loaded from cache and in that case I think `extensions.enabledScopes`
 is enforced and previously installed search extensions are disabled (the
 icons are a moz-extension:// resource and that's probably why they
 disappear, because the extension is not enabled).

 The patch in https://github.com/acatarineu/tor-browser/commit/31563 forces
 reloading the search extensions if `extensions.enabledScopes` in the cache
 has changed, and fixes the engines when switching from 1 to 5 and
 restarting the browser.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31563#comment:4>
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