UserTrackerTab.php

<?php

namespace Drupal\tracker\Plugin\Menu;

use Drupal\Core\Menu\LocalTaskDefault;
use Drupal\Core\Routing\RouteMatchInterface;

/**
 * Provides route parameters needed to link to the current user tracker tab.
 */
class UserTrackerTab extends LocalTaskDefault {
    
    /**
     * Current user object.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * Gets the current active user.
     *
     * @todo: https://www.drupal.org/node/2105123 put this method in
     *   \Drupal\Core\Plugin\PluginBase instead.
     *
     * @return \Drupal\Core\Session\AccountInterface
     */
    protected function currentUser() {
        if (!$this->currentUser) {
            $this->currentUser = \Drupal::currentUser();
        }
        return $this->currentUser;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getRouteParameters(RouteMatchInterface $route_match) {
        return [
            'user' => $this->currentUser()
                ->Id(),
        ];
    }

}