Theme Upgrader: Be super-careful and check the contents of the $wp_theme_directories variable before merging it, if someone has changed it directly, or worse, unset it, this could've resulted in the $protected_directories being empty. See [25082] See #22501


git-svn-id: https://develop.svn.wordpress.org/trunk@25180 602fd350-edb4-49c9-b593-d223f7449a82
Plugin Upgrader: Plugin_Upgrader::upgrade() returns nothing in event of success, every other install(), upgrade() and bulk_upgrade() method returns true, so return true; 


git-svn-id: https://develop.svn.wordpress.org/trunk@25181 602fd350-edb4-49c9-b593-d223f7449a82