components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/first_run/first_run.h

Index: chrome/browser/first_run/first_run.h
diff --git a/chrome/browser/first_run/first_run.h b/chrome/browser/first_run/first_run.h
index 0a03d7d5fcf410c751185cf4cacb74f4b4249e6f..24fa69c2d59d1f8243dcf45ae5a0041a1e128383 100644
--- a/chrome/browser/first_run/first_run.h
+++ b/chrome/browser/first_run/first_run.h
@@ -18,13 +18,16 @@
 
 class CommandLine;
 class GURL;
-class PrefRegistrySyncable;
 class Profile;
 
 namespace base {
 class FilePath;
 }
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 // This namespace contains the chrome first-run installation actions needed to
 // fully test the custom installer. It also contains the opposite actions to
 // execute during uninstall. When the first run UI is ready we won't
@@ -88,7 +91,7 @@ bool CreateSentinel();
 std::string GetPingDelayPrefName();
 
 // Register user preferences used by the MasterPrefs structure.
-void RegisterUserPrefs(PrefRegistrySyncable* registry);
+void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
 
 // Removes the sentinel file created in ConfigDone(). Returns false if the
 // sentinel file could not be removed.