Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/extensions/external_policy_loader.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/external_policy_loader.h"
 
 #include "base/logging.h"
 #include "base/values.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 61 matching lines @@
   }
   prefs_.reset(result);
   LoadFinished();
 }
 
 void ExternalPolicyLoader::Observe(
     int type,
     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;
-    }
-    default:
-      NOTREACHED() << "Unexpected notification type.";
+  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.";
+    }
+  }
+}
+
 }  // namespace extensions