Intermittent error in /workers/constructors/Worker/Worker-constructor.html

[jdm]

I suspect the worker is reporting an error and it's being propagated to the window's onerror handler, sometimes before onload and sometimes after.

{
    "status": "ERROR", 
    "group": "default", 
    "message": "unexpected token: ':'", 
    "stack": "http://web-platform.test:8000/workers/constructors/Worker/does-not-exist.js:1:8", 
    "subtest": null, 
    "test": "/workers/constructors/Worker/Worker-constructor.html", 
    "line": 142571, 
    "action": "test_result", 
    "expected": "OK"
}