Restart Gecko after first-run
Currently, when TBA is first launched, it installs the extensions from the configured distribution. Torbutton requires a two-stage installation process because it is not a restartless addon.
Stage 1 is: copy the.xpi into a staging directory.
Stage 2 is: on restart, Gecko installs any extensions in the staging directory.
This is a bad UX for TBA users because they do not have the protections of torbutton on first-run, and the Security Settings menu option isn't available.
I think the easiest solution is simply restarting the Gecko thread after it fully initializes and installs the extensions. The user should be going through the Onboarding screens at that time, so they shouldn't notice Gecko restarting.