Intermittent TIMEOUT in /webmessaging/with-ports/018.html, /webmessaging/without-ports/018.html

[gterzian]

{
    "status": "TIMEOUT", 
    "group": "default", 
    "message": "Test timed out", 
    "stack": null, 
    "subtest": "origin of the script that invoked the method, javascript:", 
    "test": "/webmessaging/with-ports/018.html", 
    "line": 182860, 
    "action": "test_result", 
    "expected": "PASS"
}
{
    "status": "TIMEOUT", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/webmessaging/with-ports/018.html", 
    "line": 182861, 
    "action": "test_result", 
    "expected": "OK"
}

The tests post a message to an iframe that has a JS url, and apparently the message is never received. I suspect the problem is somewhere in the navigation of the frame, as opposed to the messaging.

It could also be that the origin check fails, because those iframe do not share the origin of their creator as they should? I think this was noted either at #22888 or #22879