The loaded event should only fire when we've actually triggered a refresh. If loaded is bound when the iframe is created, sometimes the blank iframe will fire a 'load' event before a refresh is triggered (this occurred with relative frequency in firefox). By binding the loaded event in the refresh function, we prevent this from occurring.
git-svn-id: http://svn.automattic.com/wordpress/trunk@20049 1a063a9b-81f0-0310-95a4-ce76da25c4cd