gecko/toolkit/mozapps/extensions/content/blocklist.css

.hardBlockedAddon {
  -moz-binding: url("chrome://mozapps/content/extensions/blocklist.xml#hardblockedaddon");
}

.softBlockedAddon {
  -moz-binding: url("chrome://mozapps/content/extensions/blocklist.xml#softblockedaddon");
}