components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/sync/sync_prefs.h

Index: chrome/browser/sync/sync_prefs.h
diff --git a/chrome/browser/sync/sync_prefs.h b/chrome/browser/sync/sync_prefs.h
index e2598664429ed135db6913eb472d5ada5dde28aa..5b3e8cfd6cb9c1d52a4583a175adeea8d7fe0ec6 100644
--- a/chrome/browser/sync/sync_prefs.h
+++ b/chrome/browser/sync/sync_prefs.h
@@ -15,10 +15,13 @@
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/notifier/invalidation_state_tracker.h"
 
-class PrefRegistrySyncable;
 class PrefService;
 class ProfileIOData;
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 namespace browser_sync {
 
 class SyncPrefObserver {
@@ -54,7 +57,7 @@ class SyncPrefs : NON_EXPORTED_BASE(public base::NonThreadSafe),
 
   virtual ~SyncPrefs();
 
-  static void RegisterUserPrefs(PrefRegistrySyncable* registry);
+  static void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
 
   // Checks if sync is enabled for the profile that owns |io_data|. This must
   // be invoked on the IO thread, and can be used to check if sync is enabled
@@ -136,7 +139,9 @@ class SyncPrefs : NON_EXPORTED_BASE(public base::NonThreadSafe),
   void RegisterPrefGroups();
 
   static void RegisterDataTypePreferredPref(
-      PrefRegistrySyncable* prefs, syncer::ModelType type, bool is_preferred);
+      user_prefs::PrefRegistrySyncable* prefs,
+      syncer::ModelType type,
+      bool is_preferred);
   bool GetDataTypePreferred(syncer::ModelType type) const;
   void SetDataTypePreferred(syncer::ModelType type, bool is_preferred);