public static function getInstance()
 {
     if (null === self::$instance) {
         self::$instance = new self();
     }
     return self::$instance;
 }
 function setUp()
 {
     parent::setUp();
     $this->full_sync = Jetpack_Sync_Full::getInstance();
 }
 function set_defaults()
 {
     $this->sync_queue = new Jetpack_Sync_Queue('sync');
     // saved settings
     $settings = $this->get_settings();
     $this->set_dequeue_max_bytes($settings['dequeue_max_bytes']);
     $this->set_upload_max_bytes($settings['upload_max_bytes']);
     $this->set_upload_max_rows($settings['upload_max_rows']);
     $this->set_sync_wait_time($settings['sync_wait_time']);
     $this->set_full_sync_client(Jetpack_Sync_Full::getInstance());
     $this->codec = new Jetpack_Sync_Deflate_Codec();
     $this->constants_whitelist = Jetpack_Sync_Defaults::$default_constants_whitelist;
     $this->update_options_whitelist();
     $this->network_options_whitelist = Jetpack_Sync_Defaults::$default_network_options_whitelist;
     $this->taxonomy_whitelist = Jetpack_Sync_Defaults::$default_taxonomy_whitelist;
     $this->is_multisite = is_multisite();
     // theme mod varies from theme to theme.
     $this->options_whitelist[] = 'theme_mods_' . get_option('stylesheet');
     if ($this->is_multisite) {
         $this->callable_whitelist = array_merge(Jetpack_Sync_Defaults::$default_callable_whitelist, Jetpack_Sync_Defaults::$default_multisite_callable_whitelist);
     } else {
         $this->callable_whitelist = Jetpack_Sync_Defaults::$default_callable_whitelist;
     }
 }