On Android, the DNS config change signal is controlled entirely by the network change signal, but it's way slower, something like 70ms on my Pixel, because it waits to read the new config. Both of these signals fail all current HostResolverImpl::Jobs with ERR_NETWORK_CHANGED, regardless of whether the async or system resolver is used.

We could improve this by clearing the DnsConfig when we get the network change signal, allowing jobs to start using the system resolver, and then not aborting them when we get the new config read.