User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3825.0 Safari/537.36 Edg/126.96.36.199
Steps to reproduce:
See new WPT tests for Sec-Fetch-* headers added here: https://github.com/web-platform-tests/wpt/pull/17200
Setup environment to run WPT tests.
-Ctrl + Click the refresh icon to reload the test in a new tab.
The specific test case that's causing issues is adding a link element with the rel=prefetch attribute to the documents head element and performing validation during the onload event of the link element.
Some of the time (maybe 2-3/10 loads) the prefetch test case will fail unexpectedly with a different value 'assert_not_equals: got disallowed value "No header has been recorded"'
When this happens the onload event is fired which triggers validation (fetch request to the wptserv instance to validate a previous request for the prefetch resource was received). However no network request for the prefetch resource occurs either before or after the onload is fired.
The resource specified in the link element should have been requested then the onload should have fired. The test result, PASS/FAIL, should be deterministic when run multiple times.