Editor scrolling: 
- Pin the TinyMCE statusbar (elements path) to the bottom.
- Add support for pinning the menu when present.
- Add borders from CSS.
- Optimize getting most elements outerHeight.
Part props avryl, fixes #29293, see #28328.
Built from https://develop.svn.wordpress.org/trunk@29579


git-svn-id: http://core.svn.wordpress.org/trunk@29353 1a063a9b-81f0-0310-95a4-ce76da25c4cd