update_engine: Persist cohorts sent by omaha even if there's no update.
Omaha can set the cohorts in the <appid> tag even if there's no update and
update_engine should persist them. This patch fixes that case and adds a test
for it.
BUG=chromium:503728
TEST=Added unittest.
Change-Id: I23c13645557396704107a2a0c2c420f536a52b03
Reviewed-on: https://chromium-review.googlesource.com/282591
Trybot-Ready: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
2 files changed