[net] Move DnsConfigService to NetworkChangeNotifier.

net/dns/dns_config_service.cc

Index: net/dns/dns_config_service.cc
diff --git a/net/dns/dns_config_service.cc b/net/dns/dns_config_service.cc
index 2291b4ebb061d72fcc3b6021e92c9e5d20d3bfed..ed3d0df8419654a1d144bb6b60dded129a329fbf 100644
--- a/net/dns/dns_config_service.cc
+++ b/net/dns/dns_config_service.cc
@@ -81,27 +81,23 @@ DnsConfigService::DnsConfigService()
       last_sent_empty_(true) {}
 
 DnsConfigService::~DnsConfigService() {
-  // Must always clean up.
-  NetworkChangeNotifier::RemoveDNSObserver(this);
 }
 
-void DnsConfigService::Read(const CallbackType& callback) {
+void DnsConfigService::ReadConfig(const CallbackType& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK(!callback.is_null());
   DCHECK(callback_.is_null());
   callback_ = callback;
-  OnDNSChanged(NetworkChangeNotifier::CHANGE_DNS_WATCH_STARTED);
+  ReadNow();
 }
 
-void DnsConfigService::Watch(const CallbackType& callback) {
+void DnsConfigService::WatchConfig(const CallbackType& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK(!callback.is_null());
   DCHECK(callback_.is_null());
-  NetworkChangeNotifier::AddDNSObserver(this);
   callback_ = callback;
-  if (NetworkChangeNotifier::IsWatchingDNS())
-    OnDNSChanged(NetworkChangeNotifier::CHANGE_DNS_WATCH_STARTED);
-  // else: Wait until signal before reading.
+  StartWatching();
+  ReadNow();
 }
 
 void DnsConfigService::InvalidateConfig() {