1 CONSOLE WARNING: Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check http://xhr.spec.whatwg.org/.
2 CONSOLE ERROR: XMLHttpRequest cannot load http://localhost:8000/xmlhttprequest/xmlhttprequest-sync-vs-async-assertion-failure.html. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://127.0.0.1:8000' is therefore not allowed access.
5 bug 40996: Progress event should not be fired during synchronous XMLHttpRequest;
6 bug 17502: Assertion failure when trying to restart a sync XMLHttpRequest as an async one from onreadystatechange.
7 Step 1: Same origin request
12 Step 2: Cross origin request, disallowed
13 NetworkError: Failed to execute 'send' on 'XMLHttpRequest': Failed to load 'http://localhost:8000/xmlhttprequest/xmlhttprequest-sync-vs-async-assertion-failure.html'.
15 Step 3: Cross origin request, allowed
20 Step 4: Cross origin request, check that preflight isn't attempted