This is a request for an un-do of https://bugs.webkit.org/show_bug.cgi?id=104762
Per the latest ResourceTiming (Level 2) spec:
> If a resource fetch was aborted due to a networking error (e.g. DNS, TCP, or TLS error), then the fetch MAY be included as a PerformanceResourceTiming object in the Performance Timeline with initialized attribute values up to the point of failure - e.g. a TCP handshake error should report DNS timestamps for the request, and so on.
While the language says MAY, I'm requesting that failed entries (transport-level and HTTP 4xx/5xx) be included in ResourceTiming in Safari.