Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/chromeos/proxy_config_service_impl.cc

Index: chrome/browser/chromeos/proxy_config_service_impl.cc
diff --git a/chrome/browser/chromeos/proxy_config_service_impl.cc b/chrome/browser/chromeos/proxy_config_service_impl.cc
index 3b20231712fe1a377185a7c3d02e2ca269ba2aca..5eca442c92bfd7292cfaf0431d25177009de0242 100644
--- a/chrome/browser/chromeos/proxy_config_service_impl.cc
+++ b/chrome/browser/chromeos/proxy_config_service_impl.cc
@@ -586,29 +586,26 @@ void ProxyConfigServiceImpl::RegisterPrefs(PrefService* pref_service) {
 
 //------------------ ProxyConfigServiceImpl: private methods -------------------
 
-void ProxyConfigServiceImpl::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED &&
-      *(content::Details<std::string>(details).ptr()) ==
-          prefs::kUseSharedProxies) {
-    if (content::Source<PrefService>(source).ptr() == prefs()) {
-      VLOG(1) << "New use-shared-proxies = " << GetUseSharedProxies();
-      // Determine new proxy config which may have changed because of new
-      // use-shared-proxies. If necessary, activate it.
-      Network* network = NULL;
-      if (!active_network_.empty()) {
-        network = CrosLibrary::Get()->GetNetworkLibrary()->FindNetworkByPath(
-            active_network_);
-        if (!network)
-          LOG(WARNING) << "Can't find requested network " << active_network_;
-      }
-      DetermineEffectiveConfig(network, true);
+void ProxyConfigServiceImpl::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
+  DCHECK(service == prefs());
+  VLOG(1) << "New use-shared-proxies = " << GetUseSharedProxies();
+
+  if (pref_name == prefs::kUseSharedProxies) {
+    // Determine new proxy config which may have changed because of new
+    // use-shared-proxies. If necessary, activate it.
+    Network* network = NULL;
+    if (!active_network_.empty()) {
+      network = CrosLibrary::Get()->GetNetworkLibrary()->FindNetworkByPath(
+          active_network_);
+      if (!network)
+        LOG(WARNING) << "Can't find requested network " << active_network_;
     }
+    DetermineEffectiveConfig(network, true);
     return;
   }
-  PrefProxyConfigTrackerImpl::Observe(type, source, details);
+
+  PrefProxyConfigTrackerImpl::OnPreferenceChanged(service, pref_name);
 }
 
 void ProxyConfigServiceImpl::OnUISetProxyConfig() {