added a cache decorator to improve performance

lib/Drupal/views/Plugin/Type/ViewsPluginManager.php

@@ -10,6 +10,7 @@
 use Drupal\Component\Plugin\PluginManagerBase;
 use Drupal\Component\Plugin\Factory\DefaultFactory;
 use Drupal\views\Plugin\Discovery\ViewsDiscovery;
+use Drupal\Core\Plugin\Discovery\CacheDecorator;
 
 class ViewsPluginManager extends PluginManagerBase {
   /**
@@ -22,7 +23,7 @@ class ViewsPluginManager extends PluginManagerBase {
   public function __construct($type) {
     $this->type = $type;
 
-    $this->discovery = new ViewsDiscovery('views', $this->type);
+    $this->discovery = new CacheDecorator(new ViewsDiscovery('views', $this->type), 'views:' . $this->type, 'cache');
     $this->factory = new DefaultFactory($this->discovery);
   }
 }