New tab "Tiles" feature re-enabled after upgrade
After an upgrade from 5.0a3 to 5.0a4 on Linux, the browser.newtabpage.enhanced pref is still true somehow, even though we set it to false in the torbrowser prefs file. A fresh TBB 5.0a4 has the pref properly set to false on Linux.
See also legacy/trac#16316 (moved).