Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/sync/credential_cache_service_win.h

Index: chrome/browser/sync/credential_cache_service_win.h
diff --git a/chrome/browser/sync/credential_cache_service_win.h b/chrome/browser/sync/credential_cache_service_win.h
index 625f608bc58cf087e20a5c6f65dccd7d4d12dd56..1aea150616b745247971dd6117762ec94bc91de8 100644
--- a/chrome/browser/sync/credential_cache_service_win.h
+++ b/chrome/browser/sync/credential_cache_service_win.h
@@ -14,6 +14,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/json_pref_store.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/browser/sync/sync_prefs.h"
 #include "content/public/browser/notification_observer.h"
@@ -39,7 +40,8 @@ namespace syncer {
 // sync using credentials that were cached due to signing in on the other
 // (alternate) mode.
 class CredentialCacheService : public ProfileKeyedService,
-                               public content::NotificationObserver {
+                               public content::NotificationObserver,
+                               public PrefObserver {
  public:
   explicit CredentialCacheService(Profile* profile);
   virtual ~CredentialCacheService();
@@ -52,6 +54,10 @@ class CredentialCacheService : public ProfileKeyedService,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Loads cached sync credentials from the alternate profile and applies them
   // to the local profile if the load was successful.
   void ReadCachedCredentialsFromAlternateProfile();