components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/ui/ash/chrome_launcher_prefs.h

Index: chrome/browser/ui/ash/chrome_launcher_prefs.h
diff --git a/chrome/browser/ui/ash/chrome_launcher_prefs.h b/chrome/browser/ui/ash/chrome_launcher_prefs.h
index 5f68a3e6efbbe328d4240ef23a43072bc09b1206..05249da626edf6c6e3d1164ad3e15693d5f6798d 100644
--- a/chrome/browser/ui/ash/chrome_launcher_prefs.h
+++ b/chrome/browser/ui/ash/chrome_launcher_prefs.h
@@ -7,12 +7,14 @@
 
 #include <string>
 
-class PrefRegistrySyncable;
-
 namespace base {
 class DictionaryValue;
 }
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 namespace ash {
 
 // Path within the dictionary entries in the prefs::kPinnedLauncherApps list
@@ -29,7 +31,8 @@ extern const char kShelfAlignmentLeft[];
 extern const char kShelfAlignmentRight[];
 extern const char kShelfAlignmentTop[];
 
-void RegisterChromeLauncherUserPrefs(PrefRegistrySyncable* registry);
+void RegisterChromeLauncherUserPrefs(
+    user_prefs::PrefRegistrySyncable* registry);
 
 base::DictionaryValue* CreateAppDict(const std::string& app_id);