https://pantheon.corp.google.com/storage/browser/chromeos-autotest-results/165969962-chromeos-test/chromeos6-row1-rack21-host17/debug/
http://cautotest-prod.corp.google.com/afe/#tab_id=view_job&object_id=165969962

Caused CQ failure: https://uberchromegw.corp.google.com/i/chromeos/builders/quawks-paladin/builds/1793

I think this is another side effect of a flakily failing arc++ image.
But I am not able to pinpoint the problem on my own.