CL: https://chromium-review.googlesource.com/c/chromium/src/+/1385566/2
[CL is unrelated]

Failing build: https://ci.chromium.org/p/chromium/builders/luci.chromium.try/win10_chromium_x64_rel_ng/163385

Succeeding build:
https://ci.chromium.org/p/chromium/builders/luci.chromium.try/win10_chromium_x64_rel_ng/163441

Test name: 
__main__.InstallerTest.ChromeUserLevel

In the failing build, the test failed twice ['with patch', 'retry with patch', and succeeded once 'without patch'].

In the succeeding build, the test failed once ['with patch'] and succeeded twice 'without patch', 'retry with patch'

I haven't investigated deeply, but it's possible that the problem is caused by state leaking from the previous task.

Example failing tasks:
https://chromium-swarm.appspot.com/task?id=41e1e7f9b5727a10&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=41e212250724e510&refresh=10&show_raw=1

In each of the failing tasks, it seems like test_installer.py is finding a crash at the very beginning of its execution:
"""
Command: C:\b\s\w\ir\.swarming_module_cache\vpython\9ff274\Scripts\python.exe ..\..\testing\scripts\run_isolated_script_test.py --isolated-script-test-output=C:\b\s\w\iooptvf7\results.json ../../chrome/test/mini_installer/test_installer.py --output-dir=C:\b\s\w\iooptvf7 --isolated-script-test-filter=__main__.InstallerTest.ChromeUserLevel --isolated-script-test-output=C:\b\s\w\iooptvf7\output.json --isolated-script-test-perf-output=C:\b\s\w\iooptvf7\perftest-output.json

[1219/173543:test_installer.py(504)] Config found at C:\b\s\w\ir\chrome\test\mini_installer\config\config.config
[1219/173543:test_installer.py(542)] Setting --force-clean
ChromeUserLevel: no_pv -> install_chrome_user -> chrome_user_installed_not_inuse -> test_chrome_with_chromedriver_user -> chrome_user_installed_not_inuse -> uninstall_chrome_user -> clean
 ... [1219/173546:test_installer.py(190)] Verifying state no_pv
[1219/173546:test_installer.py(157)] Beginning action install_chrome_user
[1219/173553:test_installer.py(160)] Finished action install_chrome_user
[1219/173553:test_installer.py(190)] Verifying state chrome_user_installed_not_inuse
[1219/173553:test_installer.py(157)] Beginning action test_chrome_with_chromedriver_user
[1219/173557:test_installer.py(231)] stdout:
[1219/173557:test_chrome_with_chromedriver.py(85)] Saved Chrome crash dump to C:\b\s\w\iooptvf7\5f19a176-59f5-4802-9591-d62ddaf91a9a.dmp
"""

which then causes the first test to fail:
"""
[1219/165431:test_chrome_with_chromedriver.py(131)] Saved Chrome log to C:\b\s\w\io_rbw2i\tmpvdh7yq
Traceback (most recent call last):
  File "test_chrome_with_chromedriver.py", line 188, in <module>
    sys.exit(main())
  File "test_chrome_with_chromedriver.py", line 183, in main
    'The page body was not correct')
  File "C:\b\s\w\ir\.swarming_module\bin\Lib\contextlib.py", line 24, in __exit__
    self.gen.next()
  File "test_chrome_with_chromedriver.py", line 135, in CreateChromedriver
    report_count)
Exception: Failing test due to 1 crash reports found
ERROR
"""