On https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests/, WebViewInteractiveTests/WebViewInteractiveTest.LongPressSelection/1 failed frequently:
https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests/66381
https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests/66385
https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests/66395

And the flakiness dashboard confirms that:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=WebViewInteractiveTests%2FWebViewInteractiveTest.LongPressSelection%2F1&testType=site_per_process_interactive_ui_tests

Example Log:
[ RUN      ] WebViewInteractiveTests/WebViewInteractiveTest.LongPressSelection/1
Xlib:  extension "RANDR" missing on display ":99".
Fontconfig warning: "/etc/fonts/fonts.conf", line 146: blank doesn't take any effect anymore. please remove it from your fonts.conf
[7933:7933:0111/182454.259576:WARNING:password_store_factory.cc(241)] 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.
[7933:7969:0111/182454.265415:ERROR:bus.cc(394)] Failed to connect to the bus: Could not parse server address: Unknown address type (examples of valid types are "tcp" and on UNIX "unix")
LaunchProcess: failed to execvp:
xdg-desktop-menu
LaunchProcess: failed to execvp:
xdg-icon-resource
[7933:7951:0111/182454.388843:WARNING:shell_integration_linux.cc(324)] Could not install icon chrome-knkdmffkebabblbnglhcjonbdpgcjchl-Default.png at size 512.
LaunchProcess: failed to execvp:
xdg-desktop-menu
[7933:7933:0111/182454.466804:INFO:CONSOLE(9)] "Guest url is: http://localhost:38251/extensions/platform_apps/web_view/text_selection/guest.html", source: chrome-extension://knkdmffkebabblbnglhcjonbdpgcjchl/embedder.js (9)
[7933:7933:0111/182454.532219:INFO:CONSOLE(9)] "webview.onLoadStop", source: chrome-extension://knkdmffkebabblbnglhcjonbdpgcjchl/embedder.js (9)
[7933:8004:0111/182454.534145:WARNING:embedded_test_server.cc(228)] Request not handled. Returning 404: /favicon.ico
[7933:7933:0111/182454.736001:INFO:CONSOLE(7)] "GUEST_CONTEXTMENU", source: http://localhost:38251/extensions/platform_apps/web_view/text_selection/guest.html (7)
../../chrome/browser/apps/guest_view/web_view_interactive_browsertest.cc:1637: Failure
Value of: ui::TouchSelectionMenuRunner::GetInstance()->IsRunning()
  Actual: false
Expected: true
[7933:7933:0111/182454.960058:INFO:chrome_cryptauth_service.cc(233)] Profile is not authenticated yet; waiting before starting CryptAuth managers.
[  FAILED  ] WebViewInteractiveTests/WebViewInteractiveTest.LongPressSelection/1, where GetParam() = true (1326 ms)


+amaralp, Can you please help investigate/triage?