Moves the reference to the source collection out of the props model. If it was translated over to a query (which was potentially possible) which then fired an ajax request, jQuery would attempt to serialize an object recursively, which caused an infinite loop and much sadness for my browser.
see #21390.
git-svn-id: http://core.svn.wordpress.org/trunk@22737 1a063a9b-81f0-0310-95a4-ce76da25c4cd