send method
Sends a message according to its contents.
message
A message to send to the other party via FCM.
returns
A function called after the message is successfully queued for
sending. runtime.lastError
should be checked, to ensure a message was
sent without problems.
Implementation
Future<String> send(SendMessage message) async {
var $res = await promiseToFuture<String>($js.chrome.gcm.send(message.toJS));
return $res;
}