A http request issued from a local scheme like qrc is blocked because of CORS (cross-origin-resource-sharing) restriction. We expect the local scheme is not considered as cross-origin.

Attached is a repro Qt project based in example webui. It tests qrc, customized/registered scheme, and file scheme, was built and run with Qt5.15.9 and 6.3.1.

• the user defined scheme can NOT be qrc as it's an internal scheme
• even with user defined scheme (loc in the repro), the http request will be blocked.
  • js: Access to XMLHttpRequest at 'https://www.google.com/' from origin 'loc:' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
• the file scheme is working in 5.15.9 but failing with 6.3.1 in this repro. 
• likely the same issue as https://bugreports.qt.io/browse/QTBUG-76258. bur workaround didn't work anymore.
• per our investigate, this issue is also related to Chromium SameSiteByDefaultCookie flag