[whatwg] Web author docs for postMessage, updated postMessage tests

[Jeff Walden]

Jeff Walden wrote:
> == Tests ==
>
> http://web.mit.edu/jwalden/www/whatwg/postMessage-v2.zip
>
> Fourth, .origin for posts from data: URIs in Mozilla is the origin of the window that opened the data: URL, which is not what HTML5 wants 

I seem to have misread or misremembered how data: URIs are handled by HTML5, so this part was wrong; I updated the tests in the file at the above location to revert the change.  Now there's an explicit, un-Mozilla-guarded check that "http://localhost:8888" == the .origin of an event posted from a data: window to its opener which is located on <http://localhost:8888>.

Jeff