Tests that DevTools can request the content of a sandboxed iframe without a crash (crbug.com/500193041)
frame.url: http://devtools.oopif-a.test:8000/inspector-protocol/network/resources/cached.php
{
    error : {
        code : -32000
        message : No resource with given URL found
    }
    id : <number>
    sessionId : <string>
}