Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/extensions/component_loader.cc

Index: chrome/browser/extensions/component_loader.cc
diff --git a/chrome/browser/extensions/component_loader.cc b/chrome/browser/extensions/component_loader.cc
index e7e5b16e776894b5bd20e60ae34db9103925f84f..51f0acf7f10a3ea8d5185d3e2a707c63573d72d6 100644
--- a/chrome/browser/extensions/component_loader.cc
+++ b/chrome/browser/extensions/component_loader.cc
@@ -407,13 +407,9 @@ void ComponentLoader::AddDefaultComponentExtensions() {
   AddScriptBubble();
 }
 
-void ComponentLoader::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(std::string(prefs::kEnterpriseWebStoreURL),
-            *content::Details<const std::string>(details).ptr());
+void ComponentLoader::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kEnterpriseWebStoreURL), pref_name);
   AddOrReloadEnterpriseWebStore();
 }