[tbb-bugs] #16316 [Tor Browser]: Disable New Tiles feature in Tor Browser based on ESR 38

[Tor Bug Tracker & Wiki]

#16316: Disable New Tiles feature in Tor Browser based on ESR 38
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     Reporter:  gk       |      Owner:  tbb-team
         Type:  task     |     Status:  reopened
     Priority:  major    |  Milestone:
    Component:  Tor      |    Version:
  Browser                |   Keywords:  ff38-esr, tbb-linkability,
   Resolution:           |  tbb-5.0a3-essential, tbb-pref,
Actual Points:           |  TorBrowserTeam201507
       Points:           |  Parent ID:
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Comment (by mcs):

 The code that is causing trouble is a combination of
 _setDefaultEnhanced(), here:
 http://mxr.mozilla.org/mozilla-
 esr38/source/browser/modules/DirectoryLinksProvider.jsm#138
 (which is called at init time) and the pref observer that is in that same
 module:
 http://mxr.mozilla.org/mozilla-
 esr38/source/browser/modules/DirectoryLinksProvider.jsm#155

 Since at first there is no user pref value in Tor Browser,
 _setDefaultEnhanced() when called at init time sets
 browser.newtabpage.enhanced = true.  If you then set
 browser.newtabpage.enhanced = false (e.g., via about:config), the user
 pref value disappears because the browser default pref value is already
 false in Tor Browser 5.0a3.  And then when the pref. observer is invoked
 it calls _setDefaultEnhanced(), which determines that there is no user
 value and therefore sets the pref. back to true for you.  How unpleasant.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16316#comment:6>
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