Pending requests that are associated with a browser will be canceled when that
browser is destroyed. Pending requests that are not associated with a browser
(e.g. created using CefURLRequest::Create), and that use the global context, may
still be pending when CefShutdown is called. For this reason the
no_debugct_check attribute has been added for CefResourceRequestHandler and
CefCookieAccessFilter interfaces.
To test: Load a YouTube video or other long-loading content in cefclient and
close the application. No assertions trigger for leaked CefFrame objects.