diff --git a/core/includes/common.inc b/core/includes/common.inc
index be2f2a4..5f4694c 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1321,35 +1321,17 @@ function l($text, $path, array $options = array()) {
     $variables['options']['attributes']['hreflang'] = $variables['options']['language']->id;
   }
 
-  // Because l() is called very often we statically cache values that require an
-  // extra function call.
-  static $drupal_static_fast;
-  if (!isset($drupal_static_fast['active'])) {
-    $drupal_static_fast['active'] = &drupal_static(__FUNCTION__);
-  }
-  $active = &$drupal_static_fast['active'];
-  if (!isset($active)) {
-    $active = array(
-      'path' => current_path(),
-      'front_page' => drupal_is_front_page(),
-      'language' => language(Language::TYPE_URL)->id,
-      'query' => Drupal::service('request')->query->all(),
-    );
+  // Add a data-drupal-link-type attribute to let JavaScript know this link is
+  // used for navigation (as opposed to?) and so is potentially eligible for an
+  // active class.
+  if (!empty($variables['options']['query'])) {
+    $variables['options']['attributes']['data-drupal-link-query'] = json_encode($variables['options']['query']);
   }
 
-  // Determine whether this link is "active', meaning that it links to the
-  // current page. It is important that we stop checking "active" conditions if
-  // we know the link is not active. This helps ensure that l() remains fast.
-  // An active link's path is equal to the current path.
-  $variables['url_is_active'] = ($path == $active['path'] || ($path == '<front>' && $active['front_page']))
-  // The language of an active link is equal to the current language.
-  && (empty($variables['options']['language']) || $variables['options']['language']->id == $active['language'])
-  // The query parameters of an active link are equal to the current parameters.
-  && ($variables['options']['query'] == $active['query']);
-
-  // Add the "active" class if appropriate.
-  if ($variables['url_is_active']) {
-    $variables['options']['attributes']['class'][] = 'active';
+  // Add a data-drupal-link-system-path attribute to expose the system path for
+  // this link to JavaScript.
+  if (!isset($variables['options']['attributes']['data-drupal-link-system-path'])) {
+    $variables['options']['attributes']['data-drupal-link-system-path'] = Drupal::service('path.alias_manager.cached')->getSystemPath($path);
   }
 
   // Remove all HTML and PHP tags from a tooltip, calling expensive strip_tags()
@@ -2234,13 +2216,20 @@ function drupal_add_js($data = NULL, $options = NULL) {
           // @todo Make this less hacky: http://drupal.org/node/1547376.
           $scriptPath = $GLOBALS['script_path'];
           $pathPrefix = '';
+          $current_query = Drupal::service('request')->query->all();
           url('', array('script' => &$scriptPath, 'prefix' => &$pathPrefix));
-          $javascript['settings']['data'][] = array(
+          $path = array(
             'basePath' => base_path(),
             'scriptPath' => $scriptPath,
             'pathPrefix' => $pathPrefix,
             'currentPath' => current_path(),
+            'isFront' => drupal_is_front_page(),
+            'currentLanguage' => Drupal::languageManager()->getLanguage(Language::TYPE_URL)->id,
           );
+          if (!empty($current_query)) {
+            $path['currentQuery'] = (object) $current_query;
+          }
+          $javascript['settings']['data'][] = array('path' => $path);
         }
         // All JavaScript settings are placed in the header of the page with
         // the library weight so that inline scripts appear afterwards.
diff --git a/core/misc/active-link.js b/core/misc/active-link.js
new file mode 100644
index 0000000..21b5e13
--- /dev/null
+++ b/core/misc/active-link.js
@@ -0,0 +1,54 @@
+(function (Drupal, drupalSettings) {
+
+  "use strict";
+  /**
+   * Append active class.
+   *
+   * The link is only active if its path corresponds to the current path, the
+   * language of the linked path is equal to the current language, and if the
+   * query parameters of the link equal those of the current request, since the
+   * same request with different query parameters may yield a different page
+   * (e.g., pagers).
+   */
+  Drupal.behaviors.l = {
+    attach: function queryL (context) {
+      // Start by finding all potentially active links.
+      var path = drupalSettings.path;
+      var queryString = JSON.stringify(path.currentQuery);
+      var querySelector = path.currentQuery ? "[data-drupal-link-query='" + queryString + "']" : ':not([data-drupal-link-query])';
+      var originalSelectors = ['[data-drupal-link-system-path="' + path.currentPath + '"]'];
+      var selectors;
+
+      // If this is the front page, we have to check for the <front> path as well.
+      if (path.isFront) {
+        originalSelectors.push('[data-drupal-link-system-path="<front>"]');
+      }
+
+      // Add language filtering.
+      selectors = [].concat(
+        // Links without any hreflang attributes (most of them).
+        originalSelectors.map(function (selector) { return selector + ':not([hreflang])';}),
+        // Links with hreflang equals to the current language.
+        originalSelectors.map(function (selector) { return selector + '[hreflang="' + path.currentLanguage + '"]';})
+      );
+
+      // Add query string selector for pagers, exposed filters.
+      selectors = selectors.map(function (current) { return current + querySelector; });
+
+      // Query the DOM.
+      var activeLinks = context.querySelectorAll(selectors.join(','));
+      for (var i = 0, il = activeLinks.length; i < il; i += 1) {
+        activeLinks[i].classList.add('active');
+      }
+    },
+    detach: function (context, settings, trigger) {
+      if (trigger === 'unload') {
+        var activeLinks = context.querySelectorAll('a.active');
+        for (var i = 0, il = activeLinks.length; i < il; i += 1) {
+          activeLinks[i].classList.remove('active');
+        }
+      }
+    }
+  };
+
+})(Drupal, drupalSettings);
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index bdff14b..b7df052 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -625,7 +625,7 @@ Drupal.AjaxCommands.prototype = {
     if (new_content.parents('html').length > 0) {
       // Apply any settings from the returned JSON if available.
       settings = response.settings || ajax.settings || Drupal.settings;
-      Drupal.attachBehaviors(new_content, settings);
+      Drupal.attachBehaviors(new_content[0], settings);
     }
   },
 
diff --git a/core/misc/drupal.js b/core/misc/drupal.js
index 9c86a0a..b14b185 100644
--- a/core/misc/drupal.js
+++ b/core/misc/drupal.js
@@ -270,7 +270,7 @@ Drupal.t = function (str, args, options) {
  * Returns the URL to a Drupal page.
  */
 Drupal.url = function (path) {
-  return drupalSettings.basePath + drupalSettings.scriptPath + path;
+  return drupalSettings.path.basePath + drupalSettings.path.scriptPath + path;
 };
 
 /**
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 536e6d2..7d111cd 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -992,9 +992,11 @@ function system_library_info() {
     'version' => VERSION,
     'js' => array(
       'core/misc/drupal.js' => array('group' => JS_LIBRARY, 'weight' => -18),
+      'core/misc/active-link.js' => array(),
     ),
     'dependencies' => array(
       array('system', 'domready'),
+      array('system', 'drupalSettings'),
     ),
   );