Prevent stylesheets from being appended to the list more than once.

common/modules/sanitizer.jsm

@@ -1,4 +1,5 @@
 // Copyright (c) 2009 by Doug Kearns <dougkearns@gmail.com>
+// Copyright (c) 2009-2010 by Kris Maglione <maglione.k at Gmail>
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
@@ -50,7 +51,7 @@ const Sanitizer = Module("sanitizer", tmp.Sanitizer, {
             passwords: "Saved passwords",
             sessions: "Authenticated sessions",
         };
-        // These builtin methods don't support hosts or have
+        // These builtin methods don't support hosts or otherwise have
         // insufficient granularity
         this.addItem("cookies", {
             description: "Cookies",

common/modules/styles.jsm

@@ -107,12 +107,13 @@ const Styles = Module("Styles", {
             sheet.filter = filter;
             sheet.css = String(css);
         }
-        else
+        else {
             sheet = Sheet(name, this._id++, filter.filter(util.identity), String(css), system, agent);
+            sheets.push(sheet);
+        }
 
         if (!lazy)
             sheet.enabled = true;
-        sheets.push(sheet);
 
         if (name)
             names[name] = sheet;