@allada: could you please check how this works with "attach to cross-process subframes" experiment enabled? I think we should see the request twice - one canceled from the main frame and one successful from the child frame. Perhaps, it would make sense to hide canceled OOPIF requests in this case. 

FWIW, if I right-click on the subframe and inspect, then go to the Network tab in the subframe's new DevTools window, then reload the frame, the request shows up fine.  Ideally we'd transfer this status over to the devtools instance that's shown in the parent process.  I agree that at the very least, we should probably be hiding the OOPIF requests.  And perhaps we could give a hint to developers that they can get to it if they inspect the subframe?

We are working on the new mode where you inspect both main frame and all subframes in the same frontend. In this case you'll see requests from child frames right there, including the main request for cross-process subframe.

Note: I still see the red canceled request and no successful request for the OOPIF's page when using the "attach to cross-process subframes" experiment in 57.0.2971.0 (Windows Canary, using --site-per-process).

Similar issue for the Security tab of DevTools, FWIW.  For example, http://csreis.github.io/tests/cross-site-iframe-simple.html should show https://creis.github.io in the list of secure origins, but it's listed as Unknown / Canceled.