Migrate to Tor Browser based on FF52

Feature Branch: feature/12464-tor-browser-7.0

Attachments

• unsafe-browser-e10s-failure.log
• tor-browser-e10s-failure.log

Related issues

• Has duplicate #12464 (closed)
• Blocked by #11419 (closed)
• Blocks #11106
• Blocks #8917 (closed)

Original created by @anonym on 12115 (Redmine)