Bug 1169567 - always arm deferredtask, r=dao

--HG--
extra : commitid : 2mf6ZfzgWbD
extra : rebase_source : ec761f7e4888df2b570847c24ffc8acbe0a40294
extra : amend_source : 82ae359c38195bade7c4f8608dbb18bac8bd3f3a

toolkit/content/widgets/preferences.xml

@@ -1311,8 +1311,8 @@
               } else {
                 // Each time the preference is changed, restart the delay.
                 element._deferredValueUpdateTask.disarm();
-                element._deferredValueUpdateTask.arm();
               }
+              element._deferredValueUpdateTask.arm();
             }
           }
         ]]>