[tor-bugs] #16983 [Tor Browser]: Favicon requests not isolated if one opens the tab list dropdown

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#16983: Favicon requests not isolated if one opens the tab list dropdown
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     Reporter:           |      Owner:  tbb-team
  someone_else           |     Status:  needs_review
         Type:  defect   |  Milestone:
     Priority:  major    |    Version:
    Component:  Tor      |   Keywords:  tbb-linkability,
  Browser                |  TorBrowserTeam201509R
   Resolution:           |  Parent ID:
Actual Points:           |
       Points:           |
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Comment (by arthuredelstein):

 Replying to [comment:6 gk]:
 > So, this actually means there won't be any fetches anymore at all as
 long as I have the tab open (at least that's what I am seeing)?

 With this patch, the assigned isolation domain is the same for both tab
 and dropdown. So my interpretation is that the favicon.ico file is cached
 and doesn't need to be fetched again.

 > If not how could I verify that your patch is working as expected?

 You can set torbutton's `loglevel` pref to `3` to see it each request and
 its assigned isolation domain. If you see the correct favicon appear in
 both the tab and the dropdown for a given site, and you don't see any no-
 first-party fetches for the favicon file, then I would argue that the
 problem is fixed.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16983#comment:7>
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