Bug 1428676 pt 2. Test content can't use '-moz-appearance: -moz-menulist-button'. r=emilio

--HG--
extra : rebase_source : 38fbb1987f416d859a75cd3742d936aca9ac6d41

layout/style/test/test_non_content_accessible_values.html

@@ -16,6 +16,9 @@ const NON_CONTENT_ACCESSIBLE_VALUES = {
     "-moz-popup",
     "-moz-groupbox",
   ],
+  "-moz-appearance": [
+    "-moz-menulist-button",
+  ],
 };
 
 if (!SpecialPowers.getBoolPref("layout.css.xul-box-display-values.content.enabled")) {