Review vulnerability history from FF31 to FF45
The Security Slider values were set based on a review of historical vulnerabilities. We should try to skim through https://www.mozilla.org/security/known-vulnerabilities/firefox.html from FF31 to FF38 to see if any new patterns have emerged, and if we should add other prefs to the slider.
If this proves useful, we should also make this part of our rebasing process.
One tricky bit will be untangling all of the "Miscellaneous memory safety hazard" bugs..