VoidCallback should not be a class

[dgrove]

r2354

In trying to port http://playground.html5rocks.com/#simple_notifications to Dart, I want to do this:

window.webkitNotifications.requestPermission(() {});

If you look at the Dart docs, they will tell you that RequestPermission has this type signature:

void requestPermission(VoidCallback callback)

which seems just horrible.

[rakudrama]

The issue appears to be that the WebKit IDL does not mark VoidCallback with the 'Callback' extended attribute.
This change should probably be made and upstreamed.

The sample calls requestPermission with no arguments:

document.getElementById('request_permission').addEventListener('click', function() {
  window.webkitNotifications.requestPermission();
}, false);

The WebKit IDL for the requestPermissions operation has one parameter, but it is marked 'Custom'.
The parameter could be [Optional].

I have not found a corresponding w3c document to clarify the interface.

[rakudrama]

Added Fixed label.