components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.h

Index: chrome/browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.h
diff --git a/chrome/browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.h b/chrome/browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.h
index a0194a2c8998f9906fa4095f88be3ca2667cd634..d79f5f3b0c40feb967766d0468a1edd5a95bb13e 100644
--- a/chrome/browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.h
+++ b/chrome/browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.h
@@ -14,20 +14,23 @@
 #include "chromeos/dbus/dbus_method_call_status.h"
 #include "third_party/cros_system_api/dbus/service_constants.h"
 
-class PrefRegistrySyncable;
 class PrefService;
 
 namespace chromeos {
 class CryptohomeClient;
-}  // namespace chromeos
+}
 
 namespace cryptohome {
 class AsyncMethodCaller;
-}  // namespace cryptohome
+}
 
 namespace policy {
 class EnterpriseInstallAttributes;
-}  // namespace policy
+}
+
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
 
 namespace extensions {
 
@@ -80,7 +83,7 @@ typedef EPKPChallengeMachineKey
 
 class EPKPChallengeUserKey : public EPKPChallengeKeyBase {
  public:
-  static void RegisterUserPrefs(PrefRegistrySyncable* registry);
+  static void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
 
  protected:
   virtual bool RunImpl() OVERRIDE;