Inline documentation for hooks in wp-includes/class-wp-admin-bar.php

See #25229 props betzster


git-svn-id: https://develop.svn.wordpress.org/trunk@25475 602fd350-edb4-49c9-b593-d223f7449a82
Clean up the documentation for add_filter and apply_filters.

Fixes #19203 props DrewAPicture, ericlewis


git-svn-id: https://develop.svn.wordpress.org/trunk@25476 602fd350-edb4-49c9-b593-d223f7449a82