Provide a function to set the get_updates timeout to 0 for the tutorial.

(imported from commit c904360ffe6fe3cacc9de37d523501a0d45f7176)

tools/jslint/check-all.js

@@ -41,7 +41,7 @@ var globals =
     + ' scroll_to_selected get_private_message_recipient'
     + ' load_old_messages'
     + ' at_top_of_viewport at_bottom_of_viewport within_viewport'
-    + ' viewport restart_get_updates'
+    + ' viewport restart_get_updates force_get_updates'
     + ' load_more_messages reset_load_more_status have_scrolled_away_from_top'
     + ' maybe_scroll_to_selected recenter_pointer_on_display suppress_scroll_pointer_update'
     + ' process_visible_unread_messages message_range message_in_table process_loaded_for_unread'

zephyr/static/js/zephyr.js

@@ -987,6 +987,10 @@ function get_updates(options) {
     });
 }
 
+function force_get_updates() {
+    get_updates_timeout = setTimeout(get_updates, 0);
+}
+
 function load_old_messages(opts) {
     opts = $.extend({}, {
         cont_will_add_messages: false