Introduce PrefRegistrySyncable, simplifying PrefServiceSyncable.

chrome/browser/web_resource/promo_resource_service.cc

Index: chrome/browser/web_resource/promo_resource_service.cc
diff --git a/chrome/browser/web_resource/promo_resource_service.cc b/chrome/browser/web_resource/promo_resource_service.cc
index 12ede8654f0beae8afc2bed49e3915533c430125..e9f7bb3f22d5c494f7d1b1d9f83e655d215ae052 100644
--- a/chrome/browser/web_resource/promo_resource_service.cc
+++ b/chrome/browser/web_resource/promo_resource_service.cc
@@ -11,7 +11,8 @@
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/pref_registry_simple.h"
-#include "chrome/browser/prefs/pref_service_syncable.h"
+#include "chrome/browser/prefs/pref_registry_syncable.h"
+#include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/web_resource/notification_promo.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_switches.h"
@@ -67,14 +68,16 @@ void PromoResourceService::RegisterPrefs(PrefRegistrySimple* registry) {
 }
 
 // static
-void PromoResourceService::RegisterUserPrefs(PrefServiceSyncable* prefs) {
+void PromoResourceService::RegisterUserPrefs(PrefService* prefs,
+                                             PrefRegistrySyncable* registry) {
   // TODO(dbeam): remove in M28 when all prefs have been cleared.
   // http://crbug.com/168887
-  prefs->RegisterStringPref(prefs::kNtpPromoResourceCacheUpdate,
-                            "0",
-                            PrefServiceSyncable::UNSYNCABLE_PREF);
+  // TODO(joi): Remove PrefService parameter; move this to migration code.
+  registry->RegisterStringPref(prefs::kNtpPromoResourceCacheUpdate,
+                               "0",
+                               PrefRegistrySyncable::UNSYNCABLE_PREF);
   prefs->ClearPref(prefs::kNtpPromoResourceCacheUpdate);
-  NotificationPromo::RegisterUserPrefs(prefs);
+  NotificationPromo::RegisterUserPrefs(prefs, registry);
 }
 
 PromoResourceService::PromoResourceService()