CONSOLE WARNING: line 14: Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
CONSOLE ERROR: line 22: Failed to load http://www1.web-platform.test:8001/xhr/resources/access-control-basic-options-not-supported.py: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://web-platform.test:8001' is therefore not allowed access. The response had HTTP status code 400.
