Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/policy/cloud_policy_refresh_scheduler.cc

Index: chrome/browser/policy/cloud_policy_refresh_scheduler.cc
diff --git a/chrome/browser/policy/cloud_policy_refresh_scheduler.cc b/chrome/browser/policy/cloud_policy_refresh_scheduler.cc
index da011dfaf33218e603ada371fc0cb8721734df55..f1a7fe0a9d2e4b6d2e5757fd3077492d683afffa 100644
--- a/chrome/browser/policy/cloud_policy_refresh_scheduler.cc
+++ b/chrome/browser/policy/cloud_policy_refresh_scheduler.cc
@@ -99,13 +99,10 @@ void CloudPolicyRefreshScheduler::OnStoreError(CloudPolicyStore* store) {
   // error is required. NB: Changes to is_managed fire OnStoreLoaded().
 }
 
-void CloudPolicyRefreshScheduler::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(refresh_delay_.GetPrefName(),
-            *content::Details<std::string>(details).ptr());
+void CloudPolicyRefreshScheduler::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  DCHECK_EQ(refresh_delay_.GetPrefName(), pref_name);
 
   ScheduleRefresh();
 }