WebWorker onmessage parameter should be MessageEvent

[ochrons]

Currently defined as:

var onmessage: js.Function1[js.Any, _] = js.native

which prevents defining a handler function like,

    val worker = new Worker("worker.js")
    worker.onmessage = (e: dom.MessageEvent) => { }

onmessage should be defined as:

var onmessage: js.Function1[MessageEvent, _] = js.native

see https://developer.mozilla.org/en-US/docs/Web/API/Worker/onmessage

[mseddon]

Yep, this looks correct. The WebWorker draft is referential spaghetti, but it's defined in the Web Messaging API. Might be worth verifying the signature of MessageEvent hasn't changed while we're at it.

[exoego]

This can be closed since type of onmessage is fixed in #224