[whatwg] Calling HTMLDocument.open() should change the origin of the document to the caller's origin

[Jeff Walden]

The current verbiage describing open() says nothing about the document's origin reflecting that of the mutator, which is an oversight which should eventually be corrected.  This came up when considering the values of the domain/uri properties on a MessageEvent created by a document.open()ed document which calls postMessage.  Just making sure this gets in the queue to be addressed...

Jeff