Background Updates: Fix a PHP Warning caused by a Upgrader instance being passed into the Theme & Plugin $extra_stats parameter.
Background Updates: Fix two variable typos in r27905

Merges [27906], [27928] to the 3.8 branch.
Fixes #27633.


git-svn-id: https://develop.svn.wordpress.org/branches/3.8@27929 602fd350-edb4-49c9-b593-d223f7449a82