CONSOLE WARNING: line 20: 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 51: Failed to load http://www1.web-platform.test:8001/cors/resources/cors-makeheader.py?headers=x-print: Request header field y-print is not allowed by Access-Control-Allow-Headers in preflight response.
