This CQ slave run failed:
    https://luci-milo.appspot.com/buildbot/chromeos/betty-arc64-paladin/2118

The VMTest stage in the builder failed twice; this bug concerns
only the _second_ failure:
    https://pantheon.corp.google.com/storage/browser/chromeos-image-archive/betty-arc64-paladin/R67-10511.0.0-rc3/vm_test_results_2/smoke/test_harness/all/SimpleTestVerify/1_autotest_tests/results-08-platform_FilePerms

This same symptom has happened before (without becoming a CQ failure);
see this recent run:
    https://luci-milo.appspot.com/buildbot/chromeos/betty-arc64-paladin/2114

The relevant part of the logs from the most recent failure:
03/23 13:36:41.031 ERROR|platform_FilePerms:0383| No expectations entry for "/home/chronos/user" with info "{'device': '/dev/sda1', 'type': 'ext4', 'options': ['rw', 'seclabel', 'nosuid', 'nodev', 'noexec', 'noatime', 'commit=600', 'data=ordered']}"
03/23 13:36:41.039 ERROR|platform_FilePerms:0383| No expectations entry for "/run/arc/sdcard/write/emulated" with info "{'device': '/dev/fuse', 'type': 'fuse', 'options': ['rw', 'nosuid', 'nodev', 'noexec', 'noatime', 'user_id=656383', 'group_id=656383', 'default_permissions', 'allow_other']}"
03/23 13:36:41.047 ERROR|platform_FilePerms:0383| No expectations entry for "/home/chronos/u-35058812aaef879c7078532f92322900ddf34348" with info "{'device': '/dev/sda1', 'type': 'ext4', 'options': ['rw', 'seclabel', 'nosuid', 'nodev', 'noexec', 'noatime', 'commit=600', 'data=ordered']}"
03/23 13:36:41.055 ERROR|platform_FilePerms:0383| No expectations entry for "/opt/google/containers/android/rootfs/android-data" with info "{'device': '/dev/sda1', 'type': 'ext4', 'options': ['rw', 'seclabel', 'nosuid', 'nodev', 'noexec', 'noatime', 'commit=600', 'data=ordered']}"
03/23 13:36:41.063 ERROR|platform_FilePerms:0383| No expectations entry for "/run/arc/media/removable" with info "{'device': 'passthrough', 'type': 'fuse', 'options': ['rw', 'nosuid', 'nodev', 'relatime', 'user_id=1000', 'group_id=1000', 'default_permissions', 'allow_other']}"
03/23 13:36:41.070 ERROR|platform_FilePerms:0383| No expectations entry for "/run/arc/sdcard/default/emulated" with info "{'device': '/dev/fuse', 'type': 'fuse', 'options': ['rw', 'nosuid', 'nodev', 'noexec', 'noatime', 'user_id=656383', 'group_id=656383', 'default_permissions', 'allow_other']}"
03/23 13:36:41.078 ERROR|platform_FilePerms:0383| No expectations entry for "/home/root/35058812aaef879c7078532f92322900ddf34348" with info "{'device': '/dev/sda1', 'type': 'ext4', 'options': ['rw', 'seclabel', 'nosuid', 'nodev', 'noexec', 'noatime', 'commit=600', 'data=ordered']}"
03/23 13:36:41.086 ERROR|platform_FilePerms:0383| No expectations entry for "/home/user/35058812aaef879c7078532f92322900ddf34348" with info "{'device': '/dev/sda1', 'type': 'ext4', 'options': ['rw', 'seclabel', 'nosuid', 'nodev', 'noexec', 'noatime', 'commit=600', 'data=ordered']}"
03/23 13:36:41.094 ERROR|platform_FilePerms:0383| No expectations entry for "/run/arc/sdcard/read/emulated" with info "{'device': '/dev/fuse', 'type': 'fuse', 'options': ['rw', 'nosuid', 'nodev', 'noexec', 'noatime', 'user_id=656383', 'group_id=656383', 'default_permissions', 'allow_other']}"
03/23 13:36:41.102 DEBUG|              test:0410| Test failed due to Found 9 permission errors. Exception log follows the after_iteration_hooks.