Some affected builds:
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%281%29/builds/40436
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%281%29/builds/40447

Log:
[ RUN      ] KioskTest.LaunchAppWithNetworkConfigAccelerator
HTTPS server started on 127.0.0.1:46244...
sending server_data: {"host": "127.0.0.1", "port": 46244} (36 bytes)
[19510:19510:0621/052400.862633:WARNING:statistics_provider.cc(286)] Statistics loaded after waiting 5ms.
Xlib:  extension "RANDR" missing on display ":99".
[19510:19608:0621/052401.006771:WARNING:freezer_cgroup_process_manager.cc(61)] Cgroup freezer does not exist or is not writable. Unable to freeze renderer processes.
[19510:19510:0621/052401.287009:WARNING:CONSOLE(0)] "Styling master document from stylesheets defined in HTML Imports is deprecated, and is planned to be removed in M65, around March 2018. Please refer to https://goo.gl/EGXzpw for possible migration paths.", source:  (0)
[19510:19510:0621/052401.322627:WARNING:CONSOLE(1)] "This file is deprecated. Please use `iron-flex-layout/iron-flex-layout-classes.html`, and one of the specific dom-modules instead", source: chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-shadow-flex-layout-extracted.js (1)
[19510:19510:0621/052401.329886:WARNING:CONSOLE(1)] "This file is deprecated. Please use `iron-flex-layout/iron-flex-layout-classes.html`, and one of the specific dom-modules instead", source: chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout-extracted.js (1)
[19510:19510:0621/052401.850393:WARNING:CONSOLE(3866)] "/deep/ combinator is no longer supported in CSS dynamic profile. It is now effectively no-op, acting as if it were a descendant combinator. You should consider to remove it. See https://www.chromestatus.com/features/4964279606312960 for more details.", source: chrome://resources/polymer/v1_0/polymer/polymer-extracted.js (3866)
[19510:19510:0621/052402.033410:ERROR:device_event_log_impl.cc(156)] [05:24:02.033] Network: network_state_handler.cc:160 SetTechnologyEnabled() called for the Tether DeviceState, but the current state was: 0
[19510:19510:0621/052402.041339:INFO:CONSOLE(8123)] "Loading asset bundle oauth-enrollment", source: chrome://oobe/oobe.js (8123)
[19510:19510:0621/052402.045062:INFO:kiosk_browsertest.cc(219)] kiosk locked  = 1
[19510:19510:0621/052402.397644:INFO:CONSOLE(8107)] "Finished loading asset bundle oauth-enrollment", source: chrome://oobe/oobe.js (8107)
[19510:19510:0621/052402.420671:INFO:signin_screen_handler.cc(1360)] Login WebUI >> active: 1, source: gaia-signin
[19510:19510:0621/052402.445965:WARNING:signin_screen_handler.cc(974)] Login UI is not active - postponed prefs change.
[19510:19672:0621/052402.480562:ERROR:fake_gaia.cc(321)] Unhandled request /update_check.xml
[19510:19510:0621/052402.567932:ERROR:base_screen_handler_utils.cc(71)] Failed to deserialize, parse as email, valid=1
[19510:19510:0621/052402.574093:ERROR:CONSOLE(8640)] "TypeError: login.AccountPickerScreen.setOverlayColors is not a function
    at <anonymous>:1:27", source: chrome://oobe/oobe.js (8640)
[19510:19510:0621/052402.574161:ERROR:CONSOLE(1)] "Uncaught TypeError: login.AccountPickerScreen.setOverlayColors is not a function", source:  (1)
[19510:19510:0621/052402.575820:ERROR:kiosk_profile_loader.cc(112)] Cryptohome is mounted before launching kiosk app.
[19510:19510:0621/052402.589634:ERROR:configuration_policy_handler_list.cc(92)] Unknown policy: NTPContentSuggestionsEnabled
[19510:19510:0621/052402.590809:INFO:signin_screen_handler.cc(1360)] Login WebUI >> active: 0, source: gaia-signin
[19510:19510:0621/052402.590908:ERROR:configuration_policy_handler_list.cc(92)] Unknown policy: NTPContentSuggestionsEnabled
[19510:19510:0621/052402.611267:ERROR:profile_helper.cc(324)] ProfileHelper::GetProfileByUserUnsafe is called when |user|'s profile is not created. It probably means that something is wrong with a calling code. Please report in http://crbug.com/361528 if you see this message.
[19510:19510:0621/052402.611301:ERROR:profile_helper.cc(324)] ProfileHelper::GetProfileByUserUnsafe is called when |user|'s profile is not created. It probably means that something is wrong with a calling code. Please report in http://crbug.com/361528 if you see this message.
[19510:19510:0621/052402.611318:ERROR:profile_helper.cc(324)] ProfileHelper::GetProfileByUserUnsafe is called when |user|'s profile is not created. It probably means that something is wrong with a calling code. Please report in http://crbug.com/361528 if you see this message.
[19510:19649:0621/052402.628117:WARNING:startup_app_launcher.cc(142)] Can't find auth file at /b/s/w/itrPxDvb/.org.chromium.Chromium.dd9CME/dvZtf9I/kiosk_auth
[19510:19672:0621/052402.750666:ERROR:fake_gaia.cc(321)] Unhandled request /update_check.xml
[19510:19510:0621/052402.753504:WARNING:error_screen.cc(192)] Network error screen message is shown
[19510:19672:0621/052402.766224:WARNING:fake_gaia.cc(318)] Serving request /embedded/setup/chromeos
127.0.0.1 - - [21/Jun/2017 05:24:02] "GET /embedded/setup/chromeos?chrometype=chromedevice&client_id=dummytoken&client_version=61.0.3138.0&platform_version=0.0.0.0&endpoint_gen=1.0&hl=en-US HTTP/1.1" 200 -
../../chrome/browser/chromeos/login/kiosk_browsertest.cc:935: Failure
Value of: GetAppLaunchController()->showing_network_dialog()
  Actual: false
Expected: true
[19510:19510:0621/052402.926745:WARNING:pref_notifier_impl.cc(28)] Init observer found at shutdown.
[  FAILED  ] KioskTest.LaunchAppWithNetworkConfigAccelerator, where TypeParam =  and GetParam() =  (2648 ms)


I tried to reproduce locally, but could not. On the bot this flakes frequently, but mostly passes.