See https://chromium-review.googlesource.com/c/chromium/src/+/1087780 where a single bot sets "os_type" to android and gets various logdog/result-details test runner args added. We should ensure all bots have the field set. That would make CLs like https://chromium-review.googlesource.com/c/chromium/src/+/1086290 a lot more trivial.

Should also add a presubmit check to prevent new bots without that field from getting added.