[tbb-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 mcs):

 Arthur, thanks for the detailed explanation. Kathy and I understand the
 code now. But we are seeing an assertion failure in the new code inside
 ThirdPartyUtil::GetFirstPartyURIInternal() during browser startup with a
 Mac OS debug build:
  Assertion failure: IsElement(), at
 ../../../dist/include/mozilla/dom/Element.h:1369
 I will attach a stack trace, but the short story is that
 ThirdPartyUtil::GetFirstPartyIsolationURI() is being called from
 nsContentUtils::LoadImage(). The image URI is moz-
 anno:favicon:https://www.torproject.org/images/favicon.ico#-moz-
 resolution=16,16

 Maybe you need to add an IsElement() call before calling AsElement()?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16983#comment:14>
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