getCreationTime method
Retrieves the time when the InstanceID has been generated. The creation
time will be returned by the callback.
returns Function called when the retrieval completes. It should check
runtime.lastError for error when creationTime is zero.
Implementation
Future<double> getCreationTime() async {
var $res =
await promiseToFuture<double>($js.chrome.instanceId.getCreationTime());
return $res;
}