Move file and leveldb services to SequencedTaskRunners.

Bug: 
Change-Id: Ic28d2b962fc55e05a60242d3f64505ce404cc098
Reviewed-on: https://chromium-review.googlesource.com/552780
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484709}

CrOS-Libchrome-Original-Commit: cbc3df80ea6393b7f12b163dfa6baaf5675cf442
2 files changed
tree: 08929dba5eb531cc9f4b34e9d9f4877a2e92993f
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/