Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/extensions/external_policy_loader.cc

Index: chrome/browser/extensions/external_policy_loader.cc
diff --git a/chrome/browser/extensions/external_policy_loader.cc b/chrome/browser/extensions/external_policy_loader.cc
index a93fe0f6ff37ca9882e8b9672f9c019c1f7391b8..4364aad0e98ebd35f95e7ecef73f6fb933c782f0 100644
--- a/chrome/browser/extensions/external_policy_loader.cc
+++ b/chrome/browser/extensions/external_policy_loader.cc
@@ -79,28 +79,23 @@ void ExternalPolicyLoader::Observe(
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   if (profile_ == NULL) return;
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      if (content::Source<PrefService>(source).ptr() == profile_->GetPrefs()) {
-        std::string* pref_name = content::Details<std::string>(details).ptr();
-        if (*pref_name == prefs::kExtensionInstallForceList) {
-          StartLoading();
-        } else {
-          NOTREACHED() << "Unexpected preference name.";
-        }
-      }
-      break;
-    }
-    case chrome::NOTIFICATION_PROFILE_DESTROYED: {
-      if (content::Source<Profile>(source).ptr() == profile_) {
-        notification_registrar_.RemoveAll();
-        pref_change_registrar_.RemoveAll();
-        profile_ = NULL;
-      }
-      break;
+  DCHECK(type == chrome::NOTIFICATION_PROFILE_DESTROYED) <<
+      "Unexpected notification type.";
+  if (content::Source<Profile>(source).ptr() == profile_) {
+    notification_registrar_.RemoveAll();
+    pref_change_registrar_.RemoveAll();
+    profile_ = NULL;
+  }
+}
+
+void ExternalPolicyLoader::OnPreferenceChanged(PrefServiceBase* service,
+                                               const std::string& pref_name) {
+  if (service == profile_->GetPrefs()) {
+    if (pref_name == prefs::kExtensionInstallForceList) {
+      StartLoading();
+    } else {
+      NOTREACHED() << "Unexpected preference name.";
     }
-    default:
-      NOTREACHED() << "Unexpected notification type.";
   }
 }