Creates an ImageStreamCompleterHandle that will prevent this stream from being disposed at least until the handle is disposed.
Such handles are useful when an image cache needs to keep a completer alive but does not itself have a listener subscribed, or when a widget that displays an image needs to temporarily unsubscribe from the completer but may re-subscribe in the future, for example when the TickerMode changes.
Implementation
ImageStreamCompleterHandle keepAlive() {
_checkDisposed();
return ImageStreamCompleterHandle._(this);
}