Revisions: Get rid of an unneccessary ID. IDs are a bad idea.

See #24425.

git-svn-id: http://core.svn.wordpress.org/trunk@24629 1a063a9b-81f0-0310-95a4-ce76da25c4cd
When generating a background image thumbnail URL, escape percent signs for the eventual sprintf() call inside get_theme_mod().

props cfinke.
fixes #21241.



git-svn-id: http://core.svn.wordpress.org/trunk@24630 1a063a9b-81f0-0310-95a4-ce76da25c4cd