D1457: workers: don't use backgroundfilecloser in threads

[krbullock (Kevin Bullock)]

krbullock requested changes to this revision.
krbullock added a comment.
This revision now requires changes to proceed.


  Looks okay to me except for Augie's nit. @indygreg ?

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D1457

To: wlis, #hg-reviewers, indygreg, krbullock
Cc: krbullock, durin42, indygreg, mercurial-devel