Constructs a ActionManager object.
\Traversable $namespaces: An object that implements \Traversable which contains the root paths keyed by the corresponding namespace to look for plugin implementations.
public function __construct(\Traversable $namespaces) {
$this->discovery = new AnnotatedClassDiscovery('Action', $namespaces, array(), 'Drupal\\Core\\Annotation\\Action');
$this->discovery = new AlterDecorator($this->discovery, 'action_info');
$this->factory = new ContainerFactory($this);
}