Backed out 5 changesets (bug 1493104) for ESlint failure at builds/worker/checkouts/gecko/devtools/client/webide/content/addons.js on a CLOSED TREE

Backed out changeset a6cbba097c8a (bug 1493104)
Backed out changeset 8df2a288391c (bug 1493104)
Backed out changeset cb9f55dd4257 (bug 1493104)
Backed out changeset f7ecf841eb8f (bug 1493104)
Backed out changeset fa20c2c68c42 (bug 1493104)