[whatwg] Request: window.postMessage should be async

Peter Kasting wrote:
> Here's another problem an async API would automatically address: 
> https://bugzilla.mozilla.org/show_bug.cgi?id=416912

That *should* be handled by a slow-script dialog, and the fact that it isn't is simply a bug.  That the bug is triggered using postMessage is in my opinion not relevant to this discussion.

Jeff