WP_Background_Process::maybe_handle()

		public function maybe_handle() {
			// Don't lock up other requests while processing
			session_write_close();

			if ( $this->is_process_running() ) {
				// Background process already running.
				wp_die();
			}

			if ( $this->is_queue_empty() ) {
				// No data to process.
				wp_die();
			}

			check_ajax_referer( $this->identifier, 'nonce' );

			$this->handle();

			wp_die();
		}