In `WP_Filesystem_Base`, the constructor is a noop, so it shouldn't even be declared. Setting it implies that `parent::__construct()` should be called by its subclasses.

See #27881, #22234.

Built from https://develop.svn.wordpress.org/trunk@28529


git-svn-id: http://core.svn.wordpress.org/trunk@28355 1a063a9b-81f0-0310-95a4-ce76da25c4cd