From R55-8748.0.0, we started to see this error.  The build uprev Chrome from 54.0.2837.0 to 54.0.2841.0.

_GetGaiaFunction seems to wait until the following condition is true in one of iframes:
  "document.readyState == 'complete' && document.getElementById('Email') != null"

But ended up timeout and print the stack trace:

08/27 22:33:05.044 WARNI|              test:0606| Autotest caught exception when running test:
Traceback (most recent call last):
  File "/usr/local/autotest/common_lib/test.py", line 567, in _exec
    _cherry_pick_call(self.initialize, *args, **dargs)
  File "/usr/local/autotest/common_lib/test.py", line 719, in _cherry_pick_call
    return func(*p_args, **p_dargs)
  File "/usr/local/autotest/tests/cheets_PlayStoreTest/cheets_PlayStoreTest.py", line 53, in initialize
    disable_arc_opt_in=False)
  File "/usr/local/autotest/common_lib/cros/arc.py", line 361, in initialize
    **chrome_kargs)
  File "/usr/local/autotest/common_lib/cros/chrome.py", line 174, in __init__
    self._browser = browser_to_create.Create(finder_options)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/cros_browser_finder.py", line 50, in Create
    self._credentials_path)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/cros_browser_with_oobe.py", line 14, in __init__
    backend, platform_backend, credentials_path)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/browser/browser.py", line 55, in __init__
    self._browser_backend.Start()
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/cros_browser_backend.py", line 160, in Start
    self.oobe.NavigateGaiaLogin(self._username, self._password)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/oobe.py", line 73, in NavigateGaiaLogin
    self._NavigateGaiaLogin(username, password, enterprise_enroll)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/oobe.py", line 90, in _NavigateGaiaLogin
    util.WaitFor(_GetGaiaFunction, 20)(self, username, password)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/core/util.py", line 94, in WaitFor
    (timeout, GetConditionString()))
TimeoutException: Timed out while waiting 20s for _GetGaiaFunction.


Full log:

https://00e9e64bacafd5056e857792897291878855db6085e19ac1b0-apidata.googleusercontent.com/download/storage/v1/b/chromeos-autotest-results/o/74758724-chromeos-test%2Fchromeos4-row9-rack9-host1%2Fcheets_PlayStoreTest%2Fdebug%2Fcheets_PlayStoreTest.DEBUG?qk=AD5uMEt6NKOSMgEJcSoJycSeTLwtW6g496Hs3F4wGJrnj8QxpDOusKhJ3wLWU34_yethMckBieITAbLQFKzakVvSV5u1NqZPXFOa8_tzELumF5_GM0BkL1nnG7fKgTArm_QZKzL1CbECAJj5tMqpV765v2zvSwyf1GVoCFq6iKULi8WfoUIuw8pqnaDi8_mOdhP4W1amHOkIfRIn2DLq0RO27tH9r5l6gdoU44hVGi8FgUnthLq4cNYatqTfi3fALTeCswEmroudksGBY9FlH8X6NTTIdfuNaCZ_bQj0k_wyMskOs0QmAvCkpebTA7NEXCUw6uf9bWrOnAe5hw-TAHvDppuJ98JsrvHzkuG5GYuVa_eMN56dm3jNIXefwvzzx978-oFiCa3ZiwxZZhAvGIAP54J-qtW3b70ugRhIzkHf51iCKImB0n46rIWi6UtRwu3xT5ucBbGV3wJEMf7CVcovXH-sE8XDKfe0ZuF4zB-yKRrIMZFRGLP4IqQzPf4y2v0hD9UHJ5laxn9RNLIMmTDIPp02UYtNgNv_kjOUbxqOUk1IlLpmyJ6vggEMeDrz4TRJmuhRApJ7rkxKPQM1TLyZ_S0AbHuoWY1GMg2zYbv6Bc-WCmYNuX363123YADI1ALXzcVAJmAhSZFbhksAU-C-IVImwgoyPVq-DSrwySZj4Sfgwmrse4iqXMGzr0IrfGbulunEtNQbOJslGBewGNg0ZaXmkw9BF_YT4Rbiq8T4JW7W-PvcIZdpJSAVrj7dxXx2RoQSum2581RtgArLMjelHeF2_Tjj0NXrwBnb2NUtjV7F3RbCr35GFeqpUeOuYWZxX6p3kTDpAVQglhW2zvuyFfq-4ua0nlApMbqDhm_MBrdN4eddANfJXou20GxrwYRRzkv_G1SBWlaJjyWusmE2_26ucbhlA2DsPqgdoKjsifTRW4A7Oc4