`WP_Upgrader` will take any "skin" that is passed to it, and set `->skin` via composition. The default type of `->skin` is `WP_Upgrader_Skin`, which doesn't have methods declared for `->bulk_header()` and `->bulk_footer()`. Add noop methods to `WP_Upgrader_Skin`.

See #30799.

Built from https://develop.svn.wordpress.org/trunk@31122


git-svn-id: http://core.svn.wordpress.org/trunk@31103 1a063a9b-81f0-0310-95a4-ce76da25c4cd

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

@@ -137,6 +137,9 @@ class WP_Upgrader_Skin {
 				</script>';
 		}
 	}
+
+	public function bulk_header() {}
+	public function bulk_footer() {}
 }
 
 /**

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31121';
+$wp_version = '4.2-alpha-31122';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.