Constructs a \Drupal\Component\Plugin\Discovery\ProcessDecorator object.
\Drupal\Component\Plugin\Discovery\DiscoveryInterface $decorated: The discovery object that is being decorated.
callable $process_callback: The processor callback to run on each discovered definition. The callback will be called with the following arguments:
public function __construct(DiscoveryInterface $decorated, $process_callback) {
$this->decorated = $decorated;
$this->processCallback = $process_callback;
}