diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index efd7d23..89ca981 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -718,15 +718,14 @@ function theme($hook, $variables = array()) {
     if (!isset($default_attributes)) {
       $default_attributes = new Attribute();
     }
-    foreach (array('attributes', 'title_attributes', 'content_attributes') as $key) {
-      if (isset($variables[$key]) && !($variables[$key] instanceof Attribute)) {
-        if ($variables[$key]) {
-          $variables[$key] = new Attribute($variables[$key]);
-        }
-        else {
-          // Create empty attributes.
-          $variables[$key] = clone $default_attributes;
-        }
+
+    if (isset($variables['attributes']) && !($variables['attributes'] instanceof Attribute)) {
+      if ($variables['attributes']) {
+        $variables['attributes'] = new Attribute($variables['attributes']);
+      }
+      else {
+        // Create empty attributes.
+        $variables['attributes'] = clone $default_attributes;
       }
     }
 
@@ -1143,8 +1142,6 @@ function template_preprocess_datetime(&$variables) {
 
   // Add a 'datetime' class.
   $variables['attributes']['class'][] = 'datetime';
-
-  $variables['attributes'] = new Attribute($variables['attributes']);
 }
 
 /**
@@ -2035,8 +2032,6 @@ function _template_preprocess_default_variables() {
   // Variables that don't depend on a database connection.
   $variables = array(
     'attributes' => array(),
-    'title_attributes' => array(),
-    'content_attributes' => array(),
     'title_prefix' => array(),
     'title_suffix' => array(),
     'db_is_active' => !defined('MAINTENANCE_MODE'),
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index daea82c..4f56dd7 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -7,6 +7,7 @@
 
 use Drupal\block\BlockInterface;
 use Drupal\Component\Plugin\Exception\PluginException;
+use Drupal\Core\Template\Attribute;
 use Symfony\Cmf\Component\Routing\RouteObjectInterface;
 
 /**
@@ -490,6 +491,15 @@ function template_preprocess_block(&$variables) {
   if ($id = $variables['elements']['#block']->id()) {
     $variables['attributes']['id'] = drupal_html_id('block-' . $id);
   }
+
+  static $default_attributes;
+  if (!isset($default_attributes)) {
+    $default_attributes = new Attribute;
+  }
+
+  // For best performance, we only instantiate Attribute objects when needed.
+  $variables['title_attributes'] = isset($variables['title_attributes']) ? new Attribute($variables['title_attributes']) : clone $default_attributes;
+  $variables['content_attributes'] = isset($variables['content_attributes']) ? new Attribute($variables['content_attributes']) : clone $default_attributes;
 }
 
 /**
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php
index e343019..d12c88a 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php
@@ -55,7 +55,8 @@ function testBlockClasses() {
     // Test adding a class to the block content.
     $variables['content_attributes']['class'][] = 'test-class';
     template_preprocess_block($variables);
-    $this->assertEqual($variables['content_attributes']['class'], array('test-class', 'content'), 'Default .content class added to block content_attributes');
+    $classes = $variables['content_attributes']['class']->value();
+    $this->assertEqual($classes, array('test-class', 'content'), 'Default .content class added to block content_attributes');
   }
 
 }
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 1ee4ebc..533cc6a 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -12,6 +12,7 @@
 
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityChangedInterface;
+use Drupal\Core\Template\Attribute;
 use Drupal\comment\CommentInterface;
 use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
 use Drupal\field\FieldInstanceInterface;
@@ -1504,6 +1505,15 @@ function template_preprocess_comment(&$variables) {
   $variables['attributes']['data-comment-user-id'] = $comment->getOwnerId();
 
   $variables['content_attributes']['class'][] = 'content';
+
+  static $default_attributes;
+  if (!isset($default_attributes)) {
+    $default_attributes = new Attribute;
+  }
+
+  // For best performance, we only instantiate Attribute objects when needed.
+  $variables['title_attributes'] = isset($variables['title_attributes']) ? new Attribute($variables['title_attributes']) : clone $default_attributes;
+  $variables['content_attributes'] = isset($variables['content_attributes']) ? new Attribute($variables['content_attributes']) : clone $default_attributes;
 }
 
 /**
diff --git a/core/modules/field/field.module b/core/modules/field/field.module
index 0aaffb5..6b394df 100644
--- a/core/modules/field/field.module
+++ b/core/modules/field/field.module
@@ -556,16 +556,11 @@ function template_preprocess_field(&$variables, $hook) {
   if (!isset($default_attributes)) {
     $default_attributes = new Attribute;
   }
-  // The default theme implementation for fields is a function.
-  // template_preprocess() (which initializes the attributes, title_attributes,
-  // and content_attributes arrays) does not run for theme function
-  // implementations. Additionally, Attribute objects for the three variables
-  // below only get instantiated for template file implementations, and we need
-  // Attribute objects for printing in both theme functions and template files.
+
   // For best performance, we only instantiate Attribute objects when needed.
   $variables['attributes'] = isset($variables['attributes']) ? new Attribute($variables['attributes']) : clone $default_attributes;
-  $variables['title_attributes'] = isset($variables['title_attributes']) ? new Attribute($variables['title_attributes']) : clone($default_attributes);
-  $variables['content_attributes'] = isset($variables['content_attributes']) ? new Attribute($variables['content_attributes']) : clone($default_attributes);
+  $variables['title_attributes'] = isset($variables['title_attributes']) ? new Attribute($variables['title_attributes']) : clone $default_attributes;
+  $variables['content_attributes'] = isset($variables['content_attributes']) ? new Attribute($variables['content_attributes']) : clone $default_attributes;
 
   // Modules (e.g., rdf.module) can add field item attributes (to
   // $item->_attributes) within hook_entity_prepare_view(). Some field
@@ -575,7 +570,7 @@ function template_preprocess_field(&$variables, $hook) {
   // formatters leave them within $element['#items'][$delta]['_attributes'] to
   // be rendered on the item wrappers provided by theme_field().
   foreach ($variables['items'] as $delta => $item) {
-    $variables['item_attributes'][$delta] = !empty($element['#items'][$delta]->_attributes) ? new Attribute($element['#items'][$delta]->_attributes) : clone($default_attributes);
+    $variables['item_attributes'][$delta] = !empty($element['#items'][$delta]->_attributes) ? new Attribute($element['#items'][$delta]->_attributes) : clone $default_attributes;
   }
 }
 
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index c22abe3..668efae 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -707,6 +707,16 @@ function template_preprocess_node(&$variables) {
     $variables['attributes']['class'][] = 'preview';
   }
   $variables['content_attributes']['class'][] = 'content';
+
+  static $default_attributes;
+  if (!isset($default_attributes)) {
+    $default_attributes = new Attribute;
+  }
+
+  // For best performance, we only instantiate Attribute objects when needed.
+  $variables['title_attributes'] = isset($variables['title_attributes']) ? new Attribute($variables['title_attributes']) : clone $default_attributes;
+  $variables['content_attributes'] = isset($variables['content_attributes']) ? new Attribute($variables['content_attributes']) : clone $default_attributes;
+
 }
 
 /**
diff --git a/core/modules/search/search.pages.inc b/core/modules/search/search.pages.inc
index 023a825..2e29ceb 100644
--- a/core/modules/search/search.pages.inc
+++ b/core/modules/search/search.pages.inc
@@ -6,6 +6,7 @@
  */
 
 use Drupal\Core\Language\Language;
+use Drupal\Core\Template\Attribute;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
@@ -88,5 +89,14 @@ function template_preprocess_search_result(&$variables) {
   // Provide separated and grouped meta information..
   $variables['info_split'] = $info;
   $variables['info'] = implode(' - ', $info);
+
+  static $default_attributes;
+  if (!isset($default_attributes)) {
+    $default_attributes = new Attribute;
+  }
+
+  // For best performance, we only instantiate Attribute objects when needed.
+  $variables['title_attributes'] = isset($variables['title_attributes']) ? new Attribute($variables['title_attributes']) : clone $default_attributes;
+  $variables['content_attributes'] = isset($variables['content_attributes']) ? new Attribute($variables['content_attributes']) : clone $default_attributes;
 }