Twenty Fifteen: clean up skip-link-focus-fix.js, see #29799
Built from https://develop.svn.wordpress.org/trunk@29897


git-svn-id: http://core.svn.wordpress.org/trunk@29652 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Admin menu:
- Fix pinning after resizing the window.
- Merge the two DOM ready callbacks in common.js
- Fix the submenus position adjustment on focus.
See #29806
Built from https://develop.svn.wordpress.org/trunk@29898


git-svn-id: http://core.svn.wordpress.org/trunk@29653 1a063a9b-81f0-0310-95a4-ce76da25c4cd