Index: install.php
===================================================================
RCS file: /cvs/drupal/drupal/install.php,v
retrieving revision 1.142
diff -u -p -r1.142 install.php
--- install.php	10 Nov 2008 05:22:56 -0000	1.142
+++ install.php	11 Nov 2008 23:07:15 -0000
@@ -1109,10 +1109,18 @@ function install_configure_form(&$form_s
     '#weight' => 15,
   );
 
+  $form['server_settings']['cron_run_safe'] = array(
+    '#type' => 'checkbox',
+    '#title' => st('Automatically run cron'),
+    '#default_value' => TRUE,
+    '#description' => st('With this option enabled, the site will check whether cron has been run in the past @interval and automatically run it upon the next page request.', array('@interval' => format_interval(10800, 1))),
+    '#weight' => 20,
+  );
+
   $form['submit'] = array(
     '#type' => 'submit',
     '#value' => st('Save and continue'),
-    '#weight' => 15,
+    '#weight' => 30,
   );
   $form['#action'] = $url;
   $form['#redirect'] = FALSE;
@@ -1172,9 +1180,14 @@ function install_configure_form_submit($
   unset($form_state['old_values']);
   variable_set('user_email_verification', TRUE);
 
+  // Configure clean URLs.
   if (isset($form_state['values']['clean_url'])) {
     variable_set('clean_url', $form_state['values']['clean_url']);
   }
+  // Configure cron, using the default value of 3 hours, if enabled.
+  if (!empty($form_state['values']['cron_run_safe'])) {
+    variable_set('cron_safe_threshold', 10800);
+  }
   // The user is now logged in, but has no session ID yet, which
   // would be required later in the request, so remember it.
   $user->sid = session_id();
Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.247
diff -u -p -r1.247 bootstrap.inc
--- includes/bootstrap.inc	11 Nov 2008 22:39:58 -0000	1.247
+++ includes/bootstrap.inc	12 Nov 2008 00:06:59 -0000
@@ -1141,8 +1141,15 @@ function _drupal_bootstrap($phase) {
       if ($cache_mode != CACHE_AGGRESSIVE) {
         bootstrap_invoke_all('boot');
       }
-      // If there is a cached page, display it.
-      if ($cache) {
+      // Check whether we need to run cron.
+      if ($cron_treshold = variable_get('cron_safe_threshold', 0)) {
+        $cron_last = variable_get('cron_last', NULL);
+        if (!isset($cron_last) || (REQUEST_TIME - $cron_last > $cron_treshold)) {
+          $run_cron = TRUE;
+        }
+      }
+      // If there is a cached page, display it; unless we need to run cron.
+      if ($cache && !isset($run_cron)) {
         drupal_page_cache_header($cache);
         // If the skipping of the bootstrap hooks is not enforced, call hook_exit.
         if ($cache_mode != CACHE_AGGRESSIVE) {
Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.824
diff -u -p -r1.824 common.inc
--- includes/common.inc	11 Nov 2008 22:39:58 -0000	1.824
+++ includes/common.inc	11 Nov 2008 23:58:48 -0000
@@ -2728,6 +2728,14 @@ function _drupal_bootstrap_full() {
   // Load all enabled modules
   module_load_all();
 
+  // Register a safe cron run at the end of the request if needed.
+  if ($cron_treshold = variable_get('cron_safe_threshold', 0)) {
+    $cron_last = variable_get('cron_last', NULL);
+    if (!isset($cron_last) || (REQUEST_TIME - $cron_last > $cron_treshold)) {
+      register_shutdown_function('drupal_cron_run');
+    }
+  }
+
   // Let all modules take action before menu system handles the request
   // We do not want this while running update.php.
   if (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update') {
Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.104
diff -u -p -r1.104 system.admin.inc
--- modules/system/system.admin.inc	11 Nov 2008 22:39:59 -0000	1.104
+++ modules/system/system.admin.inc	12 Nov 2008 00:06:59 -0000
@@ -1700,7 +1700,6 @@ function system_date_time_lookup() {
  * @see system_settings_form()
  */
 function system_site_maintenance_settings() {
-
   $form['site_offline'] = array(
     '#type' => 'radios',
     '#title' => t('Site status'),
@@ -1716,6 +1715,14 @@ function system_site_maintenance_setting
     '#description' => t('Message to show visitors when the site is in offline mode.')
   );
 
+  $form['cron_safe_threshold'] = array(
+    '#type' => 'select',
+    '#title' => t('Automatically run cron'),
+    '#default_value' => variable_get('cron_safe_threshold', 0),
+    '#options' => array(0 => t('Never')) + drupal_map_assoc(array(3600, 10800, 21600, 43200, 86400, 604800), 'format_interval'),
+    '#description' => t('When enabled, the site will check whether cron has been run in the configured interval and automatically run it upon the next page request. For more information visit the <a href="@status-report-url">status report page</a>.', array('@status-report-url' => url('admin/reports/status'))),
+  );
+
   return system_settings_form($form);
 }