prompt() should not be rejected if the state was connected when called about remote-playback

[avayvod]

It is similar to PresentationRequest.start() which always rejects if the dialog is dismissed. Otherwise if the state is connected, promise returned by prompt() is useless.

btn.onclick = function() {
  if (v.remote.state === 'disconnected') {
    v.remote.prompt().then(switchToRemoteState, showError);
  } else {
    v.remote.prompt().then(switchToLocalState);
  }
};

The latter would be impossible if we always resolve the promise when connected.

If we really want to simplify it, we could just abandon the promise altogether and rely on the events - the website has to handle the events anyway because the connection can be initiated by the browser or dropped due to Wi-Fi - both without prompt() being called at all.

[mounirlamouri]

WebKit work in progress patch seems to also implement it the way the spec says. I guess if both you and @jernoble had no concern, let's close this.