The id attribute must return its associated service worker client's id.
Allows a service worker to send a message to a client (a Window, Worker, or SharedWorker).
Allows a service worker to send a message to a client (a Window, Worker, or SharedWorker). The message is received in the "message" event on navigator.serviceWorker.
A sequence of objects that are transferred with the message. The ownership of these objects is given to the destination side and they are no longer usable on the sending side.
The url attribute must return the context object's associated service worker client's serialized creation url.
¶4.2 Client of Service Workers 1 spec.