Clean up a few more unused globals.

chrome/browser/extensions/api/system_private/system_private_api.cc

Index: chrome/browser/extensions/api/system_private/system_private_api.cc
diff --git a/chrome/browser/extensions/api/system_private/system_private_api.cc b/chrome/browser/extensions/api/system_private/system_private_api.cc
index ec420066398c0adba71605bdc244edf07dcaea55..4a5654b760c793cd5eba708e286e41ed4fa97fc2 100644
--- a/chrome/browser/extensions/api/system_private/system_private_api.cc
+++ b/chrome/browser/extensions/api/system_private/system_private_api.cc
@@ -39,9 +39,12 @@ const char kVolumeKey[] = "volume";
 
 // System update states.
 const char kNotAvailableState[] = "NotAvailable";
-const char kUpdatingState[] = "Updating";
 const char kNeedRestartState[] = "NeedRestart";
 
+#if defined(OS_CHROMEOS)
+const char kUpdatingState[] = "Updating";
+#endif  // defined(OS_CHROMEOS)
+
 // Dispatches an extension event with |argument|
 void DispatchEvent(const std::string& event_name, base::Value* argument) {
   scoped_ptr<base::ListValue> list_args(new base::ListValue());