diff --git a/core/modules/editor/src/Plugin/Filter/EditorFileReference.php b/core/modules/editor/src/Plugin/Filter/EditorFileReference.php
index 5ebb267..96f59c2 100644
--- a/core/modules/editor/src/Plugin/Filter/EditorFileReference.php
+++ b/core/modules/editor/src/Plugin/Filter/EditorFileReference.php
@@ -8,7 +8,6 @@
 namespace Drupal\editor\Plugin\Filter;
 
 use Drupal\Component\Utility\Html;
-use Drupal\Component\Utility\NestedArray;
 use Drupal\filter\FilterProcessResult;
 use Drupal\filter\Plugin\FilterBase;
 
@@ -49,7 +48,7 @@ public function process($text, $langcode) {
           }
         }
       }
-      $result->setCacheTags(NestedArray::mergeDeepArray($all_file_cache_tags));
+      $result->addCacheTags($all_file_cache_tags);
     }
 
     return $result;
diff --git a/core/modules/filter/src/FilterProcessResult.php b/core/modules/filter/src/FilterProcessResult.php
index de40f07..c07b9a3 100644
--- a/core/modules/filter/src/FilterProcessResult.php
+++ b/core/modules/filter/src/FilterProcessResult.php
@@ -145,6 +145,19 @@ public function getCacheTags() {
   }
 
   /**
+   * Adds cache tags associated with the processed text.
+   *
+   * @param array $cache_tags
+   *   The cache tags to be added.
+   *
+   * @return $this
+   */
+  public function addCacheTags(array $cache_tags) {
+    $this->cacheTags = NestedArray::mergeDeepArray($this->cacheTags, $cache_tags);
+    return $this;
+  }
+
+  /**
    * Sets cache tags associated with the processed text.
    *
    * @param array $cache_tags
@@ -167,6 +180,19 @@ public function getAssets() {
   }
 
   /**
+   * Adds assets associated with the processed text.
+   *
+   * @param array $assets
+   *   The associated assets to be attached.
+   *
+   * @return $this
+   */
+  public function addAssets(array $assets) {
+    $this->assets = NestedArray::mergeDeepArray($this->assets, $assets);
+    return $this;
+  }
+
+  /**
    * Sets assets associated with the processed text.
    *
    * @param array $assets
@@ -189,6 +215,24 @@ public function getPostRenderCacheCallbacks() {
   }
 
   /**
+   * Adds #post_render_cache callbacks associated with the processed text.
+   *
+   * @param callable $callback
+   *   The #post_render_cache callback that will replace the placeholder with
+   *   its eventual markup.
+   * @param array $context
+   *   An array providing context for the #post_render_cache callback.
+   *
+   * @see drupal_render_cache_generate_placeholder()
+   *
+   * @return $this
+   */
+  public function addPostRenderCacheCallback($callback, array $context) {
+    $this->postRenderCacheCallbacks[$callback][] = $context;
+    return $this;
+  }
+
+  /**
    * Sets #post_render_cache callbacks associated with the processed text.
    *
    * @param array $post_render_cache_callbacks
diff --git a/core/modules/filter/src/Plugin/Filter/FilterCaption.php b/core/modules/filter/src/Plugin/Filter/FilterCaption.php
index 1b7c7e1..bccaf02 100644
--- a/core/modules/filter/src/Plugin/Filter/FilterCaption.php
+++ b/core/modules/filter/src/Plugin/Filter/FilterCaption.php
@@ -105,7 +105,7 @@ public function process($text, $langcode) {
       $result->setProcessedText(Html::serialize($dom));
 
       if ($caption_found) {
-        $result->setAssets(array(
+        $result->addAssets(array(
           'library' => array(
             'filter/caption',
           ),
diff --git a/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestAssets.php b/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestAssets.php
index 4bd93af..a7de6d9 100644
--- a/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestAssets.php
+++ b/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestAssets.php
@@ -27,7 +27,7 @@ class FilterTestAssets extends FilterBase {
    */
   public function process($text, $langcode) {
     $result = new FilterProcessResult($text);
-    $result->setAssets(array(
+    $result->addAssets(array(
       'library' => array(
         'filter/caption',
       ),
diff --git a/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestCacheTags.php b/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestCacheTags.php
index d970b83..3c03c3f 100644
--- a/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestCacheTags.php
+++ b/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestCacheTags.php
@@ -27,7 +27,8 @@ class FilterTestCacheTags extends FilterBase {
    */
   public function process($text, $langcode) {
     $result = new FilterProcessResult($text);
-    $result->setCacheTags(array('foo' => array('bar', 'baz')));
+    $result->addCacheTags(array('foo' => array('bar')));
+    $result->addCacheTags(array('foo' => array('baz')));
     return $result;
   }
 
diff --git a/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestPostRenderCache.php b/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestPostRenderCache.php
index cee058a..c8beaef 100644
--- a/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestPostRenderCache.php
+++ b/core/modules/filter/tests/filter_test/src/Plugin/Filter/FilterTestPostRenderCache.php
@@ -32,11 +32,7 @@ public function process($text, $langcode) {
       'token' => drupal_render_cache_generate_token(),
     );
     $result = new FilterProcessResult($text . '<p>' . drupal_render_cache_generate_placeholder($callback, $context, $context['token']) . '</p>');
-    $result->setPostRenderCacheCallbacks(array(
-      $callback => array(
-        $context,
-      ),
-    ));
+    $result->addPostRenderCacheCallback($callback, $context);
     return $result;
   }
 
diff --git a/core/modules/system/src/Tests/Common/RenderTest.php b/core/modules/system/src/Tests/Common/RenderTest.php
index 0d23de1..8eccba9 100644
--- a/core/modules/system/src/Tests/Common/RenderTest.php
+++ b/core/modules/system/src/Tests/Common/RenderTest.php
@@ -774,13 +774,16 @@ function testDrupalRenderRenderCachePlaceholder() {
       'token' => drupal_render_cache_generate_token(),
     );
     $callback = 'common_test_post_render_cache_placeholder';
+    $placeholder = drupal_render_cache_generate_placeholder($callback, $context, $context['token']);
+    $this->assertIdentical($placeholder, Html::normalize($placeholder), 'Placeholder unaltered by Html::normalize() which is used by FilterHtmlCorrector.');
+
     $test_element = array(
       '#post_render_cache' => array(
         $callback => array(
           $context
         ),
       ),
-      '#markup' => drupal_render_cache_generate_placeholder($callback, $context, $context['token']),
+      '#markup' => $placeholder,
       '#prefix' => '<foo>',
       '#suffix' => '</foo>'
     );