See https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=chrome_public_test_apk&builder=chromium.android%3AKitKat%20Phone%20Tester%20(rel)

Specifically:
org.chromium.chrome.browser.TabsTest#testTabSwitcherPortraitCloseButton
org.chromium.chrome.browser.TabsTest#testToolbarSwipePrevTab
org.chromium.chrome.browser.TabsTest#testToolbarSwipeNextThenPrevTab

The tests are green on the bots because we retry them 3 times. Before the last attempt, we reboot the device, which makes the final attempt successful. We should make the test pass on the 1st attempt. To see what a bot looks like that doesn't do that rebooting, see:
https://ci.chromium.org/buildbot/chromium.swarm/Android%20N5%20Swarm/?limit=200