DevToolsPixelOutputTests.TestLatencyInfoInstrumentation is flaky in browser_tests on Linux

https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/49709
https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/49702
https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/49696
...
https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/49526 (first occurrence I found)

Sample failure:
DevToolsPixelOutputTests.TestLatencyInfoInstrumentation (run #1):
[ RUN      ] DevToolsPixelOutputTests.TestLatencyInfoInstrumentation
Xlib:  extension "RANDR" missing on display ":99".
Xlib:  extension "RANDR" missing on display ":99".
[13109:13109:1130/151533.880608:WARNING:audio_manager.cc(317)] Multiple instances of AudioManager detected
[13109:13109:1130/151533.880647:WARNING:audio_manager.cc(278)] Multiple instances of AudioManager detected
[13109:13109:1130/151533.909622:WARNING:password_store_factory.cc(248)] Using basic (unencrypted) store for password storage. See https://chromium.googlesource.com/chromium/src/+/master/docs/linux_password_storage.md for more information about password storage options.
[13157:13157:1130/151534.086461:ERROR:sandbox_linux.cc(343)] InitializeSandbox() called with multiple threads in process gpu-process.
HTTP server started on http://127.0.0.1:35710...
sending server_data: {"host": "127.0.0.1", "port": 35710} (36 bytes)
[13109:13109:1130/151535.916541:ERROR:CONSOLE(57)] "Uncaught TypeError: Cannot read property 'addExtensions' of undefined", source: chrome-devtools://devtools/bundled/devtools_compatibility.js (57)
[13109:13109:1130/151536.608664:INFO:CONSOLE(1)] "DONE: waitForEvent.1", source:  (1)
[13109:13109:1130/151536.658689:INFO:CONSOLE(1)] "DONE: waitForEvent.2", source:  (1)
[13109:13109:1130/151536.664670:INFO:CONSOLE(1)] "DONE: waitForEvent.3", source:  (1)
[13109:13109:1130/151536.766939:INFO:CONSOLE(1)] "DONE: waitForEvent.4", source:  (1)
[13109:13109:1130/151536.884368:INFO:CONSOLE(1)] "DONE: waitForEvent.5", source:  (1)
[13109:13109:1130/151536.898046:INFO:CONSOLE(1)] "DONE: waitForEvent.6", source:  (1)
../../chrome/browser/devtools/devtools_sanity_browsertest.cc:140: Failure
Value of: result
  Actual: "[FAILED] Some expected events are not found: MouseDown"
Expected: "[OK]"
[  FAILED  ] DevToolsPixelOutputTests.TestLatencyInfoInstrumentation, where TypeParam =  and GetParam() =  (3833 ms)


A similar bug was opened ( Issue 670362 ) specifically for site_per_process_browser_tests.