[tbb-bugs] #23719 [Applications/Tor Browser]: Make sure WebExtensions are spared from JIT disabling in higher security settings (Medium-High)

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#23719: Make sure WebExtensions are spared from JIT disabling in higher security
settings (Medium-High)
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 Reporter:  cypherpunks               |          Owner:  tbb-team
     Type:  defect                    |         Status:  needs_information
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Major                     |     Resolution:
 Keywords:  tbb-performance           |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by cypherpunks_reply):

 You can easily observe the increase in extension initialization time with
 different security slider settings by disabling and enabling extensions in
 about:addons.  During this initialization time the browser UI is
 unresponsive.

 In normal usage (on my machine anyway) this delay mostly lengthens the
 time during startup between Tor connecting and the browser window
 appearing.

 With the security slider set to standard, uBlock Origin with most of the
 default filters enabled initializes after about 5 seconds of one cpu core
 pegged at 100%.  With the security slider set to safer, it takes 25
 seconds.

 I testd with Tor Browser 8.0, Windows 10, a quad-core 3 GHz CPU and plenty
 of free RAM.  Hardware acceleration is disabled and content processes are
 reduced to 1 although raising them to 2 did not change the browser startup
 delay or the unresponsive UI in the disable / enable scenario.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23719#comment:10>
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