diff --git a/core/includes/common.inc b/core/includes/common.inc
index 93d52fa..175267f 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -148,62 +148,6 @@
 const LOCALE_PLURAL_DELIMITER = "\03";
 
 /**
- * Adds output to the HEAD tag of the HTML page.
- *
- * This function can be called as long as the headers aren't sent. Pass no
- * arguments (or NULL for both) to retrieve the currently stored elements.
- *
- * @param $data
- *   A renderable array. If the '#type' key is not set then 'html_tag' will be
- *   added as the default '#type'.
- * @param $key
- *   A unique string key to allow implementations of hook_html_head_alter() to
- *   identify the element in $data. Required if $data is not NULL.
- *
- * @return
- *   An array of all stored HEAD elements.
- *
- * @see \Drupal\Core\Render\Element\HtmlTag::preRenderHtmlTag()
- *
- * @deprecated in Drupal 8.0.x, will be removed before Drupal 8.0.0
- *   Use #attached on render arrays.
- */
-function _drupal_add_html_head($data = NULL, $key = NULL) {
-  $stored_head = &drupal_static(__FUNCTION__, array());
-
-  if (isset($data) && isset($key)) {
-    if (!isset($data['#type'])) {
-      $data['#type'] = 'html_tag';
-    }
-    $stored_head[$key] = $data;
-  }
-  return $stored_head;
-}
-
-/**
- * Retrieves output to be displayed in the HEAD tag of the HTML page.
- *
- * @param bool $render
- *   If TRUE render the HEAD elements, otherwise return just the elements.
- *
- * @return string|array
- *   Return the rendered HTML head or the elements itself.
- *
- * @deprecated in Drupal 8.0.x, will be removed before Drupal 8.0.0
- *   Use #attached on render arrays.
- */
-function drupal_get_html_head($render = TRUE) {
-  $elements = _drupal_add_html_head();
-  \Drupal::moduleHandler()->alter('html_head', $elements);
-  if ($render) {
-    return \Drupal::service('renderer')->renderPlain($elements);
-  }
-  else {
-    return $elements;
-  }
-}
-
-/**
  * Prepares a 'destination' URL query parameter for use with url().
  *
  * Used to direct the user back to the referring page after completing a form.
@@ -464,39 +408,6 @@ function base_path() {
 }
 
 /**
- * Adds a LINK tag with a distinct 'rel' attribute to the page's HEAD.
- *
- * This function can be called as long the HTML header hasn't been sent, which
- * on normal pages is up through the preprocess step of _theme('html'). Adding
- * a link will overwrite a prior link with the exact same 'rel' and 'href'
- * attributes.
- *
- * @param $attributes
- *   Associative array of element attributes including 'href' and 'rel'.
- * @param $header
- *   Optional flag to determine if a HTTP 'Link:' header should be sent.
- *
- * @deprecated in Drupal 8.0.x, will be removed before Drupal 8.0.0
- *   Use #attached on render arrays.
- */
-function _drupal_add_html_head_link($attributes, $header = FALSE) {
-  $element = array(
-    '#tag' => 'link',
-    '#attributes' => $attributes,
-  );
-  $href = $attributes['href'];
-
-  if ($header) {
-    // Also add a HTTP header "Link:".
-    $href = '<' . SafeMarkup::checkPlain($attributes['href']) . '>;';
-    unset($attributes['href']);
-    $element['#attached']['http_header'][] = array('Link',  $href . drupal_http_header_attributes($attributes), TRUE);
-  }
-
-  _drupal_add_html_head($element, 'html_head_link:' . $attributes['rel'] . ':' . $href);
-}
-
-/**
  * Deletes old cached CSS files.
  *
  * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
@@ -615,6 +526,9 @@ function drupal_merge_attached(array $a, array $b) {
  *
  * @throws LogicException
  *   When attaching something of a non-existing attachment type.
+ *
+ * @deprecated in Drupal 8.0.0, will be removed before Drupal 9.0.0. Specify
+ *   attached resources and directives in the render array.
  */
 function drupal_process_attached(array $elements) {
   // Asset attachments are handled by \Drupal\Core\Asset\AssetResolver.
@@ -628,16 +542,16 @@ function drupal_process_attached(array $elements) {
       // Limit the amount allowed entries.
       switch ($callback) {
         case 'html_head':
-          // @todo Remove validation in https://www.drupal.org/node/2477223
+          // @todo Removed in https://www.drupal.org/node/2477223
           break;
         case 'feed':
-          // @todo Remove validation in https://www.drupal.org/node/2477223
+          // @todo Removed in https://www.drupal.org/node/2477223
           break;
         case 'html_head_link':
-          // @todo Remove validation in https://www.drupal.org/node/2477223
+          // @todo Removed in https://www.drupal.org/node/2477223
           break;
         case 'http_header':
-          // @todo Remove validation in https://www.drupal.org/node/2477223
+          // @todo Removed in https://www.drupal.org/node/2467759
           break;
         default:
           throw new \LogicException(sprintf('You are not allowed to use %s in #attached', $callback));
diff --git a/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php b/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
index 5841ea4..b5b3c27 100644
--- a/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
+++ b/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
@@ -124,16 +124,33 @@ public function processAttachments(AttachmentsInterface $response) {
     // it's not present.
     if (!empty($placeholders['head'])) {
 
-      // feed is a special casse of html_head_link.
+      // feed is a special casse of html_head_link. We create an html_head_link
+      // for the RSS feed.
       if (!empty($attached['feed'])) {
+        // @todo: Determine if feed is supposed to be a single structure or an
+        // array of structures.
         $feed = $attached['feed'];
-        $feed_link = [
-          'href' => $feed[0],
-          'rel' => 'alternate',
-          'title' => $feed[1],
-          'type' => 'application/rss+xml',
-        ];
-        $attached['html_head_link'][] = $feed_link;
+
+        if (is_array($feed[0])) {
+          foreach ($feed as $item) {
+            $feed_link = [
+              'href' => $item[0],
+              'rel' => 'alternate',
+              'title' => empty($feed[1]) ? '' : $item[1],
+              'type' => 'application/rss+xml',
+            ];
+            $attached['html_head_link'][] = [$feed_link];
+          }
+        }
+        else {
+          $feed_link = [
+            'href' => $feed[0],
+            'rel' => 'alternate',
+            'title' => empty($feed[1]) ? '' : $feed[1],
+            'type' => 'application/rss+xml',
+          ];
+          $attached['html_head_link'][] = $feed_link;
+        }
       }
 
       // html_head_link is a special case of html_head which can be present as
@@ -142,9 +159,15 @@ public function processAttachments(AttachmentsInterface $response) {
       // http_header keys of #attached, so we must address it first.
       if (!empty($attached['html_head_link'])) {
         $link_attached = $this->processHtmlHeadLink($attached['html_head_link']);
-        // Merge $link_attached so that its html_head and http_header
-        // sections are present for further processing.
-        $attached = array_merge($attached, $link_attached);
+        // Merge $link_attached into $attached so that its html_head and
+        // http_header values are present for further processing. The merge
+        // requires a full render array, so we have to add #attached keys.
+        $attached = $this->renderer->mergeBubbleableMetadata(
+          ['#attached' => $attached],
+          ['#attached' => $link_attached]
+        );
+        // Unwrap the #attached key.
+        $attached = $attached['#attached'];
       }
 
       // Now we can process html_head.
@@ -156,7 +179,7 @@ public function processAttachments(AttachmentsInterface $response) {
       }
     }
 
-    // Now replace the placeholders in the response content with the real data.
+    // Replace the placeholders in the response content with the real data.
     $this->renderPlaceholders($response, $placeholders, $variables);
 
     // Set the HTTP headers on the response if any bubbled.