Core Auto Updates: Add a initial skin to allow capturing the output from the upgrader without displaying it (such as we need during cron calls).

This has been copied almost verbatim from the automatic-updater plugin with a few style tweaks and additional upgrade-possible check. See #22704

Built from https://develop.svn.wordpress.org/trunk@25228


git-svn-id: http://core.svn.wordpress.org/trunk@25198 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-upgrader-skins.php

@@ -526,4 +526,80 @@ class Theme_Upgrader_Skin extends WP_Upgrader_Skin {
 		if ( ! empty($update_actions) )
 			$this->feedback(implode(' | ', (array)$update_actions));
 	}
+}
+
+/**
+ * Upgrader Skin for Background WordPress Upgrades
+ *
+ * This skin is designed to be used when no output is intended, all output 
+ * is captured and stored for the caller to process and log/email/discard.
+ *
+ * @package WordPress
+ * @subpackage Upgrader
+ * @since 3.7.0
+ */
+class Background_Upgrader_Skin extends WP_Upgrader_Skin {
+	var $messages = array();
+
+	function request_filesystem_credentials( $error = false ) {
+		// TODO: fix up request_filesystem_credentials(), or split it, to allow us to request a no-output version
+		// This will output a credentials form in event of failure, We don't want that, so just hide with a buffer
+		ob_start();
+		set_current_screen( 'tools' ); // Only here to avoid PHP Notices from screen_icon() which is used within that HTML
+		$result = parent::request_filesystem_credentials( $error );
+		ob_end_clean();
+		return $result;
+	}
+
+	function feedback( $data ) {
+		if ( is_wp_error( $data ) )
+			$string = $data->get_error_message();
+		else if ( is_array( $data ) )
+			return;
+		else
+			$string = $data;
+
+		if ( ! empty( $this->upgrader->strings[ $string ] ) )
+			$string = $this->upgrader->strings[ $string ];
+
+		if ( strpos( $string, '%' ) !== false ) {
+			$args = func_get_args();
+			$args = array_splice( $args, 1 );
+			if ( ! empty( $args ) )
+				$string = vsprintf( $string, $args );
+		}
+
+		$string = trim( $string );
+
+		// Only allow basic HTML in the messages, as it'll be used in emails/logs rather than direct browser output.
+		$string = wp_kses( $string, array(
+			'a' => array(
+				'href' => true
+			),
+			'br' => true,
+			'em' => true,
+			'strong' => true,
+		) );
+
+		if ( empty( $string ) )
+			return;
+
+		$this->messages[] = $string;
+	}
+
+	function header() {
+		ob_start();
+	}
+
+	function footer() {
+		$output = ob_get_contents();
+		if ( ! empty( $output ) )
+			$this->feedback( $output );
+		ob_end_clean();
+	}
+
+	function bulk_header() {}
+	function bulk_footer() {}
+	function before() {}
+	function after() {}
 }