core/includes/theme.inc                            |    6 ++---
 .../Drupal/system/Controller/SystemController.php  |   24 +++++++++++++-------
 .../Drupal/system/Tests/Batch/ProcessingTest.php   |   12 +++++-----
 .../Tests/System/DefaultMobileMetaTagsTest.php     |    6 ++---
 .../modules/batch_test/batch_test.callbacks.inc    |    2 +-
 5 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index b26c75a..cc2f1de 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1305,8 +1305,7 @@ function theme_links($variables) {
           }
 
           // Add a "data-drupal-link-query" attribute to let the
-          // drupal.active-link library know the query in a standardized
-          // manner.
+          // drupal.active-link library know the query in a standardized manner.
           if (!empty($link['query'])) {
             $query = $link['query'];
             ksort($query);
@@ -1321,8 +1320,7 @@ function theme_links($variables) {
           }
 
           // Add a "data-drupal-link-system-path" attribute to let the
-          // drupal.active-link library know the path in a standardized
-          // manner.
+          // drupal.active-link library know the path in a standardized manner.
           $li_attributes['data-drupal-link-system-path'] = \Drupal::service('path.alias_manager.cached')->getSystemPath($path);
         }
 
diff --git a/core/modules/system/lib/Drupal/system/Controller/SystemController.php b/core/modules/system/lib/Drupal/system/Controller/SystemController.php
index d25554dc..259ef66 100644
--- a/core/modules/system/lib/Drupal/system/Controller/SystemController.php
+++ b/core/modules/system/lib/Drupal/system/Controller/SystemController.php
@@ -184,7 +184,7 @@ public function themeSetDefault() {
    */
   public static function setLinkActiveClass(array $element, array $context) {
     // Ensure we only manipulate HTML markup.
-    if (substr($element['#markup'], 0, 9) !== '<!DOCTYPE') {
+    if (strpos($element['#markup'], '<!DOCTYPE') !== 0) {
       return $element;
     }
 
@@ -195,29 +195,37 @@ public static function setLinkActiveClass(array $element, array $context) {
     }
 
     // Build XPath query to find links that should get the "active" class.
-    $query = '//*[';
+    $query = "//*[";
     // An active link's path is equal to the current path.
-    $query .= '@data-drupal-link-system-path="' . $context['path'] . '"';
+    $query .= "@data-drupal-link-system-path='" . $context['path'] . "'";
     if ($context['front']) {
-      $query .= ' or @data-drupal-link-system-path="<front>"';
+      $query .= " or @data-drupal-link-system-path='<front>'";
     }
     // The language of an active link is equal to the current language.
     if ($context['language']) {
-      $query .= ' and (not(@hreflang) or @hreflang="' . $context['language'] . '")';
+      $query .= " and (not(@hreflang) or @hreflang='" . $context['language'] . "')";
     }
     // The query parameters of an active link are equal to the current
     // parameters.
     if ($context['query']) {
-      $query .= ' and @data-drupal-link-query="' . Json::encode($context['query']) . '"';
+      $query .= " and @data-drupal-link-query='" . Json::encode($context['query']) . "'";
     }
-    $query .= ']';
+    else {
+      $query .= " and not(@data-drupal-link-query)";
+    }
+    $query .= "]";
 
     // Set the "active" class on all matching HTML elements.
     $dom = new \DOMDocument();
     @$dom->loadHTML($element['#markup']);
     $xpath = new \DOMXPath($dom);
     foreach ($xpath->query($query) as $node) {
-      $node->setAttribute('class', $node->getAttribute('class') . ' active');
+      $class = $node->getAttribute('class');
+      if (strlen($class) > 0) {
+        $class .= ' ';
+      }
+      $class .= 'active';
+      $node->setAttribute('class', $class);
     }
     $element['#markup'] = $dom->saveHTML();
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Batch/ProcessingTest.php b/core/modules/system/lib/Drupal/system/Tests/Batch/ProcessingTest.php
index de63b73..f6c4644 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Batch/ProcessingTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Batch/ProcessingTest.php
@@ -250,28 +250,28 @@ function _resultMessages($id) {
 
     switch ($id) {
       case 'batch_0':
-        $messages[] = 'results for batch 0<br />none';
+        $messages[] = 'results for batch 0<br>none';
         break;
 
       case 'batch_1':
-        $messages[] = 'results for batch 1<br />op 1: processed 10 elements';
+        $messages[] = 'results for batch 1<br>op 1: processed 10 elements';
         break;
 
       case 'batch_2':
-        $messages[] = 'results for batch 2<br />op 2: processed 10 elements';
+        $messages[] = 'results for batch 2<br>op 2: processed 10 elements';
         break;
 
       case 'batch_3':
-        $messages[] = 'results for batch 3<br />op 1: processed 10 elements<br />op 2: processed 10 elements';
+        $messages[] = 'results for batch 3<br>op 1: processed 10 elements<br>op 2: processed 10 elements';
         break;
 
       case 'batch_4':
-        $messages[] = 'results for batch 4<br />op 1: processed 10 elements';
+        $messages[] = 'results for batch 4<br>op 1: processed 10 elements';
         $messages = array_merge($messages, $this->_resultMessages('batch_2'));
         break;
 
       case 'batch_5':
-        $messages[] = 'results for batch 5<br />op 1: processed 10 elements. $context[\'finished\'] > 1 returned from batch process, with success.';
+        $messages[] = 'results for batch 5<br>op 1: processed 10 elements. $context[\'finished\'] > 1 returned from batch process, with success.';
         break;
 
       case 'chained':
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php b/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php
index ba0889f..aaaf2bd 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php
@@ -22,9 +22,9 @@ public static function getInfo() {
   function setUp() {
     parent::setUp();
     $this->default_metatags = array(
-      'MobileOptimized' => '<meta name="MobileOptimized" content="width" />',
-      'HandheldFriendly' => '<meta name="HandheldFriendly" content="true" />',
-      'viewport' => '<meta name="viewport" content="width=device-width" />',
+      'MobileOptimized' => '<meta name="MobileOptimized" content="width"',
+      'HandheldFriendly' => '<meta name="HandheldFriendly" content="true"',
+      'viewport' => '<meta name="viewport" content="width=device-width"',
     );
   }
 
diff --git a/core/modules/system/tests/modules/batch_test/batch_test.callbacks.inc b/core/modules/system/tests/modules/batch_test/batch_test.callbacks.inc
index 6d9a9a6..ca1ea6f 100644
--- a/core/modules/system/tests/modules/batch_test/batch_test.callbacks.inc
+++ b/core/modules/system/tests/modules/batch_test/batch_test.callbacks.inc
@@ -94,7 +94,7 @@ function _batch_test_finished_helper($batch_id, $success, $results, $operations)
     $messages[] = t('An error occurred while processing @op with arguments:<br />@args', array('@op' => $error_operation[0], '@args' => print_r($error_operation[1], TRUE)));
   }
 
-  drupal_set_message(implode('<br />', $messages));
+  drupal_set_message(implode('<br>', $messages));
 }
 
 /**