The following base_unittests tests fail when ran as root on Ubuntu, but succeed when ran as a less-privileged user.

FileUtilTest.ChangeFilePermissionsAndWrite
FileUtilTest.ChangeDirectoryPermissionsAndEnumerate
FileUtilTest.ChangeFilePermissionsAndRead
TaskSchedulerWorkerTest.BumpPriorityOfAliveThreadDuringShutdown

I think it makes sense to make these tests root/user-agnostic. For context, I'm working on enabling this suite on ChromeOS, and our current setup only supports running tests inside the cros env as root. Consequently, these tests fail:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/chromeos-amd64-generic-rel-vm-tests/2666

Filing as low-pri since I'm working on adding support for non-root users to the test harness.