http://stackoverflow.com/questions/13346746/document-readystate-on-domcontentloaded
http://www.cnblogs.com/stephenykk/archive/2013/06/06/3121060.html
document.readyState on DOMContentLoaded?,布布扣,bubuko.com
document.readyState on DOMContentLoaded?
原文：http://www.cnblogs.com/daishuguang/p/3595498.html