Several HWTests and VMTests on daisy_skate and lumpy are failing with "EvaluateException: Cannot find default execution context":

desktopui_ExitOnSupervisedUserCrash
login_Cryptohome
login_LoginSuccess
login_LogoutProcessCleanup
video_ChromeHWDecodeUsed
video_ChromeRTCHWDecodeUsed
video_VideoSanity

Relevant snippet from the logs:

04/07 02:27:36.130 ERROR|           browser:0061| Failure while starting browser backend.
Traceback (most recent call last):
  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 140, in Start
    self._gaia_id, not self.browser_options.disable_gaia_services)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/oobe.py", line 55, in NavigateFakeLogin
    enterprise_enroll)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/oobe.py", line 39, in _ExecuteOobeApi
    self.WaitForJavaScriptExpression("typeof Oobe == 'function'", 20)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 98, in WaitForJavaScriptExpression
    util.WaitFor(IsJavaScriptExpressionTrue, timeout)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/core/util.py", line 86, in WaitFor
    res = condition()
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 91, in IsJavaScriptExpressionTrue
    return bool(self.EvaluateJavaScript(expr))
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 162, in EvaluateJavaScript
    expr, context_id=None, timeout=timeout)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 190, in EvaluateJavaScriptInContext
    expr, context_id=context_id, timeout=timeout)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 32, in inner
    return func(inspector_backend, *args, **kwargs)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 203, in EvaluateJavaScript
    return self._runtime.Evaluate(expr, context_id, timeout)
  File "/usr/local/telemetry/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_runtime.py", line 47, in Evaluate
    raise exceptions.EvaluateException(res['error']['message'])
EvaluateException: Cannot find default execution context
04/07 02:27:36.785 ERROR|          parallel:0026| child process failed