Issue #2087243 by olli: Fixed Views block category is double escaped with autocomplete.

core/modules/block/lib/Drupal/block/Controller/CategoryAutocompleteController.php

@@ -59,8 +59,7 @@ public function autocomplete(Request $request) {
     $matches = array();
     foreach ($this->blockManager->getCategories() as $category) {
       if (stripos($category, $typed_category) === 0) {
-        $category = String::checkPlain($category);
-        $matches[$category] = $category;
+        $matches[$category] = String::checkPlain($category);
       }
     }
     return new JsonResponse($matches);

core/modules/block/tests/Drupal/block/Tests/CategoryAutocompleteTest.php

@@ -63,9 +63,9 @@ public function setUp() {
   public function testAutocompleteSuggestions($string, $suggestions) {
     $suggestions = array_map(function ($suggestion) {
       return String::checkPlain($suggestion);
-    }, $suggestions);
+    }, MapArray::copyValuesToKeys($suggestions));
     $result = $this->autocompleteController->autocomplete(new Request(array('q' => $string)));
-    $this->assertSame(MapArray::copyValuesToKeys($suggestions), json_decode($result->getContent(), TRUE));
+    $this->assertSame($suggestions, json_decode($result->getContent(), TRUE));
   }
 
   /**