Builds and returns the renderable array for this block plugin.
array A renderable array representing the content of the block.
Overrides BlockPluginInterface::build
\Drupal\block\BlockRenderController
public function build() {
list($plugin, $derivative) = explode(':', $this
->getPluginId());
// Derivatives are prefixed with 'menu-'.
$menu = substr($derivative, 5);
return menu_tree($menu);
}