Hi whatwg, I've added a proposal to the wiki <http://wiki.whatwg.org/wiki/AllowSeamless> about letting a document indicate that it is willing to be displayed seamlessly with a cross-origin parent. This proposal is a refinement of the approach previously discussed in this thread: <http://old.nabble.com/crossorigin-property-on-iframe-td33677754.html>.
Let me know if you have any feedback. Thanks! Adam
