Provide contextual links for all entity types

src/EntityViewBuilder.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\entity\EntityViewBuilder.
+ */
+
+namespace Drupal\entity;
+
+use Drupal\Core\Entity\ContentEntityInterface;
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityViewBuilder as CoreEntityViewBuilder;
+
+/**
+ * Provides a entity view builder with contextual links support
+ */
+class EntityViewBuilder extends CoreEntityViewBuilder {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function alterBuild(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display, $view_mode) {
+    $entity_type_id = $entity->getEntityTypeId();
+    if (($entity instanceof ContentEntityInterface && $entity->isDefaultRevision()) || !$entity->getEntityType()->isRevisionable()) {
+      $build['#contextual_links'][$entity_type_id] = [
+        'route_parameters' => [
+          $entity_type_id => $entity->id()
+        ],
+      ];
+    }
+    else {
+      $build['#contextual_links'][$entity_type_id . '_revision'] = [
+        'route_parameters' => [
+          $entity_type_id => $entity->id(),
+          $entity_type_id . '_revision' => $entity->getRevisionId(),
+        ],
+      ];
+    }
+  }
+
+}