Failure seems to be in GeolocationServiceUnitTest.GeolocationConfig:
[30592:30728:1204/182729.032129:3919816197:ERROR:wifi_data_provider_chromeos.cc(138)] ScheduleStart called with uninitialized NetworkHandler
[30592:30728:1204/182729.063530:3919816443:FATAL:wifi_data_provider_chromeos.cc(130)] Check failed: started_.

Flakiness dashboard link:

It suggests that it sometimes fails with the CHECK on non-*San builds too.
Example:
https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8928293630293677744/+/steps/services_unittests/0/stdout

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f33c5b5198ade6a8dd8fc5dd02109a69fc807817

commit f33c5b5198ade6a8dd8fc5dd02109a69fc807817
Author: Pavol Marko <pmarko@chromium.org>
Date: Wed Dec 05 14:32:09 2018

Disable GeolocationServiceUnitTest.GeolocationConfig on Chrome OS

The test seems to be flaky on Chrome OS, especially on *San. Disable it
for now.

TBR=mcasas@chromium.org

Bug: 912057
Test: services_unittests
Change-Id: I9bc355d046c139fb7d27f5b2e49b87442a53120c
Reviewed-on: https://chromium-review.googlesource.com/c/1363275
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Pavol Marko <pmarko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613961}
[modify] https://crrev.com/f33c5b5198ade6a8dd8fc5dd02109a69fc807817/services/device/geolocation/geolocation_service_unittest.cc

Removing sheriff label as the flaky test has been disabled and the bug is assigned.