[REG 5.15.2 -> 5.15.3] QWebEnginePage::loadFinished signal is not emitted if the page is loaded but the server sends 404 http status code

I can reproduce this issue with widget when error page is enabled. It is reproducible with the following links:

• http://gstatic.com
• http://secureserver.net

If the navigation results 400 or greater http status code, WebEngine considers it is a load failure. If load failure happens, the widget API emits the loadFinished signal when the load of the error page is finished.

The problem is that the loading of an error page doesn't depend on the http status code thus error page should not be expected on an http error. The server may send the page with an http error code and Chromium successfully loads the page. This case, error page is not loaded and loadFinished signal is not emitted.