This is preparation to switch swarming client.

Bug: chromium:894045, chromium:907585
Change-Id: I3cd5eec0ed8a81eefbac0061f0ee0eb38f5bfd7c
Reviewed-on: https://chromium-review.googlesource.com/c/1365212Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58085}