Twenty Thirteen: create new image size for galleries, at 300 x 300 so that "large" image size doesn't load for a resulting thumbnail on index views. See #24307.

git-svn-id: http://core.svn.wordpress.org/trunk@24333 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Properly escape source parameter in audio/video shortcodes. See #23282.


git-svn-id: http://core.svn.wordpress.org/trunk@24334 1a063a9b-81f0-0310-95a4-ce76da25c4cd