Findit identified the culprit r579650 with confidence 70.0% in the config "chromium.chromiumos / linux-chromeos-rel"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVyowELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCJtY2hyb21pdW0uY2hyb21pdW1vcy9saW51eC1jaHJvbWVvcy1yZWwvMTIwNDUvY2hyb21ldm94X3Rlc3RzL1FtRmphMmR5YjNWdVpGUmxjM1F1VG1GMmFXZGhkR2x2YmtWelkyRndaWE5GWkdsMAwLEhNNYXN0ZXJGbGFrZUFuYWx5c2lzGAEM

If the culprit above is wrong, please file a bug using this link and hit submit:
https://bugs.chromium.org/p/chromium/issues/entry?status=Unconfirmed&labels=Pri-1,Test-Findit-Wrong&components=Tools%3ETest%3EFindit%3EFlakiness&summary=%5BFindit%5D%20Flake%20Analyzer%20-%20Wrong%20result%20for%20BackgroundTest.NavigationEscapesEdit&comment=Link%20to%20Analysis%3A%20https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVyowELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCJtY2hyb21pdW0uY2hyb21pdW1vcy9saW51eC1jaHJvbWVvcy1yZWwvMTIwNDUvY2hyb21ldm94X3Rlc3RzL1FtRmphMmR5YjNWdVpGUmxjM1F1VG1GMmFXZGhkR2x2YmtWelkyRndaWE5GWkdsMAwLEhNNYXN0ZXJGbGFrZUFuYWx5c2lzGAEM

Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e34c4d59cabc333defc0e25775faf43261ba6a53

commit e34c4d59cabc333defc0e25775faf43261ba6a53
Author: Jennifer Apacible <apacible@chromium.org>
Date: Fri Aug 17 18:28:09 2018

Disable flaky test.

NOTRY=true (disabling tests)

Bug:  875137 , 622387
TBR: dtseng@chromium.org
Change-Id: I625e4bcf454fb7dcdf67e83cfbe2ac643d9d8c7e
Reviewed-on: https://chromium-review.googlesource.com/1179974
Commit-Queue: apacible <apacible@chromium.org>
Reviewed-by: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584132}
[modify] https://crrev.com/e34c4d59cabc333defc0e25775faf43261ba6a53/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs

BackgroundTest.ShowContextMenu is also failed.

https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-rel/12219

../../chrome/test/base/extension_js_browser_test.cc:65: Failure
Failed
Failed: RUN_TEST_F("BackgroundTest","ShowContextMenu")
TypeError: Cannot read property 'focus' of null
    at BackgroundTest.<anonymous> (file:///b/s/w/ir/out/Release/test_data/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs:9585:28)
    at CallbackHelper.<anonymous> (file:///b/s/w/ir/out/Release/test_data/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs:8398:16)
    at CallFunctionAction.invoke (file:///b/s/w/ir/out/Release/test_data/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs:7888:22)
    at RunAllAction.invoke (file:///b/s/w/ir/out/Release/test_data/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs:8049:35)
    at file:///b/s/w/ir/out/Release/test_data/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs:8408:14
    at Object.listener [as callback] (file:///b/s/w/ir/out/Release/test_data/chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs:8609:21)
    at Object.fireEventListeners_ (extensions::automationNode:817:22)
    at Object.dispatchEventAtCapturing_ (extensions::automationNode:778:12)
    at Object.dispatchEvent (extensions::automationNode:745:14)
    at Object.onAccessibilityEvent (extensions::automationNode:1372:22)