In some cases, when InterceptingResourceHandler swaps out the old ResourceHandler with a new one, it sends a payload to the old handler.  When it does this, it doesn't send a 0-byte EOF OnReadCompleted to the old handler, unlike what we do with real successful requests.

Since the ResourceHandlers being swapped out don't care about this message don't care about the final 0-byte read, nothing bad happens, but it still seems problematic.

It would be nice if we could remove the 0-byte read notification in favor of just a success notification, but the MimeSniffingResourceHandler defers the request on that read to pass information about the read downstream.  We can't just remove the completion messages, because RedirectToFileHandler defers that.  Unclear if we can move them both onto deferring the same event, and get rid of the other one / make the other one non-deferrable.