duvall@, can you help with this one? if not please make it as available.

Looked into this one a bit further.  I think it's safe to call this a non-blocker for canary.  By directly using the async resolver, the code bypasses the shared cache.  Not using the shared cache; not a canary blocker.

Assigning to ericorth@ as per email discussion. Eric: if you only intended to enhance the network service and want me to make changes to dns_probe_runner.cc can you block this issue on another bug and assign this back to me? thx.

Sorry, assigning back fell through the cracks, but yes, I only intended to do the work on the network service side.

As of some recent improvements in HostResolver, this should now be unblocked and ready for migration.  The general idea is that this should all be possible using NetworkContext::CreateHostResolver() calls and passing DnsConfigOverrides with the relevant configuration changes.  Watching for changes to the system and reapplying the overrides over new configs should now all be handled automatically by the service.  And NetworkService::GetDnsConfigChangeManager() allows just enough listening capabilities to know when to clear the prober's cache.

Let me know if there are any issues or if I've missed any needed functionality.

Returning to available status as I probably won't have time to do this before the holiday break.