From [1] chrome_20181121-155822, It looks like the error is caused by "Gaia webview error: ERR_INTERNET_DISCONNECTED". The build log can be found from [2].

[1212:1212:1121/155830.425394:INFO:signin_screen_handler.cc(1470)] Login WebUI >> active: 1, source: gaia-signin
[1212:1212:1121/155830.519772:VERBOSE1:signin_screen_handler.cc(1424)] Login WebUI >> loginVisible, src: oobe, webui_visible_: 0
[1212:1212:1121/155830.604507:VERBOSE1:gaia_screen_handler.cc(655)] Auth extension finished loading
[1212:1212:1121/155830.605399:VERBOSE1:signin_screen_handler.cc(1424)] Login WebUI >> loginVisible, src: gaia-loading, webui_visible_: 1
[1212:1212:1121/155830.700564:WARNING:CONSOLE(2651)] "Could not find style data in module named", source: chrome://resources/polymer/v1_0/polymer/polymer-extracted.js (2651)
[1212:1212:1121/155831.069279:ERROR:gaia_screen_handler.cc(686)] Gaia webview error: ERR_INTERNET_DISCONNECTED
[1212:1212:1121/155831.069481:WARNING:signin_screen_handler.cc(791)] Retry frame load due to reason: frame error
[1212:1212:1121/155831.069830:WARNING:error_screen.cc(202)] Network error screen message is shown
[1212:1212:1121/155831.069978:VERBOSE1:gaia_screen_handler.cc(508)] Skipping reloading of Gaia since network state=offline
[1212:1212:1121/155831.075262:WARNING:CONSOLE(287)] "<webview>: The load has aborted with error -106: ERR_INTERNET_DISCONNECTED.", source: extensions::webViewEvents (287)
[1212:1212:1121/155831.153274:INFO:signin_screen_handler.cc(1470)] Login WebUI >> active: 0, source: gaia-signin
[1212:1212:1121/155831.594070:VERBOSE1:gaia_screen_handler.cc(873)] Gaia is loaded
[1212:1212:1121/155831.594276:VERBOSE1:signin_screen_handler.cc(1424)] Login WebUI >> loginVisible, src: gaia-signin, webui_visible_: 1
[1212:1212:1121/155833.162626:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1212:1121/155833.188286:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1212:1121/155833.190305:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1212:1121/155833.191318:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1212:1121/155833.266812:WARNING:CONSOLE(287)] "<webview>: The load has aborted with error -3: ERR_ABORTED.", source: extensions::webViewEvents (287)
[1212:1212:1121/155833.372335:VERBOSE1:signin_screen_handler.cc(591)] OnNetworkReady() call.
[1212:1212:1121/155833.372735:WARNING:signin_screen_handler.cc(775)] Retry frame load since network has been changed.
[1212:1212:1121/155833.372824:WARNING:error_screen.cc(212)] Network error screen message is hidden
[1212:1212:1121/155833.372908:VERBOSE1:gaia_screen_handler.cc(514)] Reloading Gaia.
[1212:1212:1121/155833.372953:VERBOSE1:gaia_screen_handler.cc(1238)] LoadAuthExtension, force: 1, offline: 0
[1212:1212:1121/155833.387446:INFO:signin_screen_handler.cc(1470)] Login WebUI >> active: 1, source: gaia-signin
[1212:1212:1121/155833.390289:WARNING:error_screen.cc(212)] Network error screen message is hidden
[1212:1212:1121/155833.390363:VERBOSE1:gaia_screen_handler.cc(502)] Skipping reloading of Gaia since gaia is loading.
[1212:1212:1121/155833.426905:VERBOSE1:signin_screen_handler.cc(1424)] Login WebUI >> loginVisible, src: gaia-loading, webui_visible_: 1
[1212:1212:1121/155833.427098:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1212:1121/155833.429593:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1438:1121/155833.519519:WARNING:spdy_session.cc(3152)] Received HEADERS for invalid stream 1
[1212:1212:1121/155833.615621:VERBOSE1:gaia_screen_handler.cc(655)] Auth extension finished loading
[1212:1212:1121/155833.616800:ERROR:CONSOLE(217)] "Unexpected condition on chrome://oobe/gaia-signin: Could not find value for languageList", source: chrome://resources/js/load_time_data.js (217)
[1212:1212:1121/155833.646283:WARNING:CONSOLE(287)] "<webview>: The load has aborted with error -3: ERR_ABORTED.", source: extensions::webViewEvents (287)
[1212:1212:1121/155833.685323:WARNING:CONSOLE(287)] "<webview>: The load has aborted with error -20: ERR_BLOCKED_BY_CLIENT.", source: extensions::webViewEvents (287)
[1212:1438:1121/155833.917633:WARNING:spdy_session.cc(3152)] Received HEADERS for invalid stream 1
[1212:1212:1121/155833.926843:ERROR:tab_manager_delegate_chromeos.cc(384)] Failed to set oom_score_adj to 300 for focused tab, pid: 2800
[1212:1438:1121/155833.932790:WARNING:spdy_session.cc(3152)] Received HEADERS for invalid stream 3
[1212:1212:1121/155836.248520:VERBOSE1:gaia_screen_handler.cc(873)] Gaia is loaded
[1212:1212:1121/155836.248664:VERBOSE1:signin_screen_handler.cc(1424)] Login WebUI >> loginVisible, src: gaia-signin, webui_visible_: 1


[1]:https://stainless.corp.google.com/browse/chromeos-autotest-results/259829140-chromeos-test/

[2]: https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8929211585559891840