Intermittent failures in /resource-timing/resource_TAO_origin.htm

[jdm]

{
    "status": "FAIL", 
    "group": "default", 
    "message": "assert_true: responseEnd should not be 0 in timing-allow cross-origin request. expected true got false", 
    "stack": "test_greater_than/<@http://web-platform.test:8000/resource-timing/resources/webperftestharness.js:141:27\nTest.prototype.step@http://web-platform.test:8000/resources/testharness.js:1594:20\ntest@http://web-platform.test:8000/resources/testharness.js:544:21\nwp_test@http://web-platform.test:8000/resource-timing/resources/webperftestharness.js:57:5\ntest_greater_than@http://web-platform.test:8000/resource-timing/resources/webperftestharness.js:141:5\nonload_test@http://web-platform.test:8000/resource-timing/resource_TAO_origin.htm:43:5\n", 
    "subtest": "responseEnd should not be 0 in timing-allow cross-origin request.", 
    "test": "/resource-timing/resource_TAO_origin.htm", 
    "line": 66551, 
    "action": "test_result", 
    "expected": "PASS"
}

We should revisit this test as part of fixing #21270.