From https://build.chromium.org/p/chromium.fyi/builders/ClangToTWin64%28dll%29%20tester/builds/4185:

[ RUN      ] AtomicFlagTest.SetOnDifferentSequenceDeathTest
../../base/synchronization/atomic_flag_unittest.cc(23): error: Death test: flag->Set()
    Result: failed to die.
 Error msg:
[  DEATH   ] [5488:5152:0912/081404.808:21657041:WARNING:test_suite.cc(235)] Test launcher output path C:\Users\CHROME~2\AppData\Local\Temp\972_13399\test_results.xml exists. Not adding test launcher result printer.
[  DEATH   ]
[  FAILED  ] AtomicFlagTest.SetOnDifferentSequenceDeathTest (37 ms)


This has been failing since the beginning of September.