Example builder: https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Android%20x64%20Builder%20%28dbg%29

Graph of disk usage: https://viceroy.corp.google.com/chrome_infra/Machines/per_machine?hostname=swarm976-c4&duration=1d&refresh=-1

This builder has failed multiple times in a row. I suspect that swarming is doing something like:
  * Delete <small && required> caches until < threshold
  * Run task
  * Run out of disk space

There's some big, honking caches that are available for deletion on this bot (everything not ending with _v2): https://chromium-swarm.appspot.com/bot?id=swarm976-c4&sort_stats=total%3Adesc

Marking as P1 as this is actually causing infra failures around the fleet, currently. If there's a systemic fix we can implement in swarming quickly, that would be the best, otherwise we can whack-a-mole.