[tbb-bugs] #21876 [Applications/Tor Browser]: e10s is not enabled on Linux (and probably OS X) by default in ESR 52 based nightlies

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#21876: e10s is not enabled on Linux (and probably OS X) by default in ESR 52 based
nightlies
-------------------------------------------------+-------------------------
 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Very High                            |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Major                                |     Resolution:
 Keywords:  ff52-esr, tbb-7.0-must-alpha,        |  Actual Points:
  TorBrowserTeam201704R                          |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------
Changes (by mcs):

 * status:  new => needs_review
 * keywords:  ff52-esr, tbb-7.0-must-alpha, TorBrowserTeam201704 =>
     ff52-esr, tbb-7.0-must-alpha, TorBrowserTeam201704R


Comment:

 Here is a patch that will cause e10s to be enabled by default, except on
 Windows XP (where Mozilla does not enable it by default either):
  https://gitweb.torproject.org/user/brade/tor-
 browser.git/commit/?h=bug21876-01&id=b9af94a7458e111efa474c32bb0a6955bb5dbc8f

 Since it looks like the fix for
 https://bugzilla.mozilla.org/show_bug.cgi?id=1348576 is not going to be
 backported to the ESR, Kathy and I like the simple approach we used in
 this patch: treat all update channels as if they are esr for e10s-related
 things.

 We also reviewed the e10srollout system extension code as well as the code
 inside `toolkit/mozapps/extensions/internal/E10SAddonsRollout.jsm`. We did
 not see anything that we are concerned about: the e10srollout extension
 sets preferences that are then used by other parts of the Firefox code.
 The "esrA" policy that we will be using consists of:
  * Windows: Don't enable e10s if accessibility APIs were used recently.
  * Windows: Don't enable e10s on WindowsXP.
  * Don't enable e10s if any incompatible add-ons are installed.
 There are also prefs that users can set to change the behavior, e.g., set
 `browser.tabs.remote.force-enable` to `true`.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21876#comment:16>
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