$task = craft()->tasks->createTask('Reroute', 'Importing routes', array(
    'files' => $files,
    'steps' => count($files)
));

class RerouteTask extends BaseTask
{
    public function getTotalSteps()
    {
        return $this->getSettings()->steps;
    }

class RerouteTask extends BaseTask
{

  protected function defineSettings()
  {
    // Files passed from controller
      return array(
        'files' => AttributeType::Mixed,
      );
  }

  public function getTotalSteps()
  {
    return count( $this->getSettings()->files );
  }

$task = craft()->tasks->createTask('Reroute', 'Importing routes', array(
  'files' => $files
));