components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/ui/webui/flags_ui.h

Index: chrome/browser/ui/webui/flags_ui.h
diff --git a/chrome/browser/ui/webui/flags_ui.h b/chrome/browser/ui/webui/flags_ui.h
index d0c912fb2007cd935a2b34698ee76844326729fc..4b268362f81bb60b7884b7f1d3aac1ae15ad37bf 100644
--- a/chrome/browser/ui/webui/flags_ui.h
+++ b/chrome/browser/ui/webui/flags_ui.h
@@ -14,13 +14,16 @@
 #endif
 
 class PrefRegistrySimple;
-class PrefRegistrySyncable;
 class Profile;
 
 namespace base {
 class RefCountedMemory;
 }
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 class FlagsUI : public content::WebUIController {
  public:
   explicit FlagsUI(content::WebUI* web_ui);
@@ -30,7 +33,7 @@ class FlagsUI : public content::WebUIController {
       ui::ScaleFactor scale_factor);
   static void RegisterPrefs(PrefRegistrySimple* registry);
 #if defined(OS_CHROMEOS)
-  static void RegisterUserPrefs(PrefRegistrySyncable* registry);
+  static void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
 #endif
 
  private: