[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..ff1bb1d4091f316a7bab138fcd7ebed8272a197f 100644
--- a/net/dns/dns_config_service.cc
+++ b/net/dns/dns_config_service.cc
@@ -75,33 +75,30 @@ base::Value* DnsConfig::ToValue() const {
 
 
 DnsConfigService::DnsConfigService()
-    : have_config_(false),
+    : watch_failed_(false),
+      have_config_(false),
       have_hosts_(false),
       need_update_(false),
       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.
+  watch_failed_ = !StartWatching();
+  ReadNow();
 }
 
 void DnsConfigService::InvalidateConfig() {
@@ -175,7 +172,7 @@ void DnsConfigService::OnHostsRead(const DnsHosts& hosts) {
 
 void DnsConfigService::StartTimer() {
   DCHECK(CalledOnValidThread());
-  if (last_sent_empty_) {
+  if (last_sent_empty_ && !watch_failed_) {
     DCHECK(!timer_.IsRunning());
     return;  // No need to withdraw again.
   }
@@ -200,7 +197,7 @@ void DnsConfigService::StartTimer() {
 
 void DnsConfigService::OnTimeout() {
   DCHECK(CalledOnValidThread());
-  DCHECK(!last_sent_empty_);
+  DCHECK(!last_sent_empty_ || watch_failed_);
   // Indicate that even if there is no change in On*Read, we will need to
   // update the receiver when the config becomes complete.
   need_update_ = true;
@@ -211,6 +208,8 @@ void DnsConfigService::OnTimeout() {
 }
 
 void DnsConfigService::OnCompleteConfig() {
+  if (watch_failed_)
+    return;  // Let it time out.

[mmenke, 2012/08/31 15:05:59]

Should we stop the timer if |needs_update_| is false?

[szym, 2012/08/31 15:55:57]

I see. The idea is to not signal anything if we have not detected a real change.

Sticking with the OnTimeout approach would also require that we don't set
|need_update_ = true| in OnTimeout if watch_failed_, and that we reset
need_update_ to false at some point.

I think it's probably less confusing to just |callback_.Run(DnsConfig())| if
|watch_failed_| is true.

I updated the tests to expect immediate notifications rather than time outs.

[mmenke, 2012/08/31 16:04:03]

I agree - think that this is the less confusing solution.

   timer_.Stop();
   if (!need_update_)
     return;