diff --git a/core/modules/views/src/Plugin/views/cache/CachePluginBase.php b/core/modules/views/src/Plugin/views/cache/CachePluginBase.php
index bdcb31b..d747283 100644
--- a/core/modules/views/src/Plugin/views/cache/CachePluginBase.php
+++ b/core/modules/views/src/Plugin/views/cache/CachePluginBase.php
@@ -238,7 +238,10 @@ public function cacheStart() {
   }
 
   /**
-   * Gather the JS/CSS from the render array, the html head from the band data.
+   * Gather the JS/CSS from the render array and the html head from band data.
+   *
+   * @param array $render_array
+   *   The view render array to collect data from.
    */
   protected function gatherHeaders(array $render_array = []) {
     // Simple replacement for head
diff --git a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
index 5e9965a..02fffa3 100644
--- a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
+++ b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
@@ -426,7 +426,7 @@ public function usesAreas() {
    * @param string $display_id
    *   The display to attach to.
    * @param array $build
-   *   The main view render array
+   *   The parent view render array.
    */
   public function attachTo(ViewExecutable $view, $display_id, array &$build) { }
 
@@ -2138,6 +2138,8 @@ public function render() {
     $element = array(
       '#theme' => $this->themeFunctions(),
       '#view' => $this->view,
+      // Assigned by reference so anything added in $element['#attached'] will
+      // be available on the view.
       '#attached' => &$this->view->element['#attached'],
       '#pre_render' => [[$this, 'elementPreRender']],
       '#rows' => $rows,
@@ -2147,19 +2149,21 @@ public function render() {
   }
 
   /**
-   * Pre render callback for view display rendering.
+   * #pre_render callback for view display rendering.
    *
    * @see self::render()
    *
    * @param array $element
+   *   The element to #pre_render
    *
    * @return array
+   *   The processed element.
    */
-  public function elementPreRender($element) {
+  public function elementPreRender(array $element) {
     $view = $element['#view'];
     $empty = empty($view->result);
 
-    // Force a render array so CSS/JS can be added.
+    // Force a render array so CSS/JS can be attached.
     if (!is_array($element['#rows'])) {
       $element['#rows'] = array('#markup' => $element['#rows']);
     }
diff --git a/core/modules/views/tests/src/Unit/Plugin/field/CounterTest.php b/core/modules/views/tests/src/Unit/Plugin/field/CounterTest.php
index e03be68..72516cf 100644
--- a/core/modules/views/tests/src/Unit/Plugin/field/CounterTest.php
+++ b/core/modules/views/tests/src/Unit/Plugin/field/CounterTest.php
@@ -86,8 +86,8 @@ protected function setUp() {
     $this->view->display_handler = $this->display;
     $this->view->pager = $this->pager;
 
-    foreach (ViewTestData::dataSet() as $count => $set) {
-      $this->testData[] = new ResultRow($set + ['index' => $count]);
+    foreach (ViewTestData::dataSet() as $index => $set) {
+      $this->testData[] = new ResultRow($set + ['index' => $index]);
     }
 
     $this->definition = array('title' => 'counter field', 'plugin_type' => 'field');