bug 580302 - Incorrect reference to Services in stylePanel.jsm, r=gavin

browser/base/content/stylePanel.jsm

@@ -54,6 +54,9 @@ var EXPORTED_SYMBOLS = ["style"];
 
 const Cc = Components.classes;
 const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+Cu.import("resource://gre/modules/Services.jsm");
 
 var style = {