Fix bug 455939 - Offline cache should synchronize in the background (hang every 4 minutes). r=philipp

calendar/providers/caldav/calDavCalendar.js

@@ -360,6 +360,8 @@ calDavCalendar.prototype = {
                 break;
             case "organizerCN":
                 return null; // xxx todo
+	    case "cache.updateTimer":
+	        return getPrefSafe("calendar.autorefresh.timeout");
             case "itip.transport":
                 if (this.hasAutoScheduling) {
                     return null;