https://chromium-review.googlesource.com/c/chromium/src/+/732841 (pending at time of writing) introduces an optimization where cache entries that 
have headers that provide for no way of reuse (zero max age, no etag or last-modified) are not opened, replacing the expensive open operation with a more asynchronous doom + create sequence, which can be overlapped with network request for the resource.  That breaks the command-line-flag enableable option of letting users open stale versions of resources from error page when HTML pages meet that criterion, since they get doomed as useless on first attempt.