Intermittent TIMEOUT in /webmessaging/with-ports/017.html, /webmessaging/without-ports/017.html #24486

{
    "status": "TIMEOUT", 
    "group": "default", 
    "message": "Test timed out", 
    "stack": null, 
    "subtest": "origin of the script that invoked the method, about:blank", 
    "test": "/webmessaging/with-ports/017.html", 
    "line": 226232, 
    "action": "test_result", 
    "expected": "PASS"
}
{
    "status": "TIMEOUT", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/webmessaging/with-ports/017.html", 
    "line": 226233, 
    "action": "test_result", 
    "expected": "OK"
}