Issue #3486050 by grimreaper, pdureau: POC Layout Builder: fix d&d and UI Styles support

Closes #3486050

modules/ui_patterns_layouts/src/Element/ComponentAlterer.php

@@ -4,7 +4,6 @@ namespace Drupal\ui_patterns_layouts\Element;
 
 use Drupal\Core\Render\Element;
 use Drupal\Core\Security\TrustedCallbackInterface;
-use Drupal\Core\Template\Attribute;
 
 /**
  * Alter the rendering of a component element.
@@ -39,9 +38,8 @@ class ComponentAlterer implements TrustedCallbackInterface {
       foreach (Element::children($element[$region_id]) as $block_id) {
         $element["#slots"][$region_id][$block_id] = $element[$region_id][$block_id];
       }
-      if (isset($element[$region_id]['#attributes']) && isset($element['#slots'][$region_id])) {
-        $element['#region_attributes'][$region_id] = new Attribute($element[$region_id]['#attributes']);
-        // Support for drag&drop and other attributes manipulation.
+      // Support for drag&drop and other attributes manipulation in preview.
+      if ($element['#layout']->isInPreview() && isset($element[$region_id]['#attributes']) && isset($element['#slots'][$region_id])) {
         $element['#slots'][$region_id] = [
           '#type' => 'html_tag',
           '#tag' => 'div',