components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/ui/prefs/prefs_tab_helper.h

Index: chrome/browser/ui/prefs/prefs_tab_helper.h
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.h b/chrome/browser/ui/prefs/prefs_tab_helper.h
index 0edc4790fa21bb660cfa4cc64f6c0eb59d620b71..72a89add69406d9b746041ed1ef32b9ba0ff1006 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.h
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.h
@@ -12,7 +12,6 @@
 #include "content/public/browser/web_contents_user_data.h"
 
 class OverlayUserPrefStore;
-class PrefRegistrySyncable;
 class PrefService;
 class Profile;
 
@@ -20,6 +19,10 @@ namespace content {
 class WebContents;
 }
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 // Per-tab class to handle user preferences.
 class PrefsTabHelper : public content::NotificationObserver,
                        public content::WebContentsUserData<PrefsTabHelper> {
@@ -27,7 +30,7 @@ class PrefsTabHelper : public content::NotificationObserver,
   virtual ~PrefsTabHelper();
 
   static void InitIncognitoUserPrefStore(OverlayUserPrefStore* pref_store);
-  static void RegisterUserPrefs(PrefRegistrySyncable* registry);
+  static void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
   static void MigrateUserPrefs(PrefService* prefs);
 
  protected: