Core class used for upgrading/installing a local set of files via the Filesystem Abstraction classes from a Zip file.

Construct the upgrader with a skin.

Clears the directory where this item is going to be installed into.

Creates a lock using WordPress options.

Download a package.

Flatten the results of WP_Filesystem_Base::dirlist() for iterating over.

Connect to the filesystem.

Add the generic strings to WP_Upgrader::$strings.

Initialize the upgrader.

Install a package.