diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1641,6 +1641,8 @@
  *     http://www.w3.org/TR/WCAG-TECHS/H42.html for more information.
  */
 function theme_links($variables) {
+  $language_url = language(Language::TYPE_URL);
+
   $links = $variables['links'];
   $attributes = $variables['attributes'];
   $heading = $variables['heading'];
@@ -1708,8 +1710,25 @@
         $link_element['#ajax'] = $link['ajax'];
       }
 
-      // Handle links.
-      if (isset($link['route_name']) || isset($link['href'])) {
+      // Handle links and ensure that the active class is added on the LIs.
+      if (isset($link['route_name'])) {
+        $variables = array(
+          'options' => array(),
+        );
+        if (!empty($link['language'])) {
+          $variables['options']['language'] = $link['language'];
+        }
+        if (\Drupal::linkGenerator()->isRouteActive($link['route_name'], $link['route_parameters'], $variables)) {
+          $class[] = 'active';
+        }
+        $item = drupal_render($link_element);
+      }
+      elseif (isset($link['href'])) {
+        $is_current_path = ($link['href'] == current_path() || ($link['href'] == '<front>' && drupal_is_front_page()));
+        $is_current_language = (empty($link['language']) || $link['language']->id == $language_url->id);
+        if ($is_current_path && $is_current_language) {
+          $class[] = 'active';
+        }
         $item = drupal_render($link_element);
       }
       // Handle title-only text items.
reverted:
--- b/core/modules/comment/comment.local_tasks.yml
+++ a/core/modules/comment/comment.local_tasks.yml
@@ -1,14 +1,14 @@
 comment.permalink_tab:
+  route_name: comment_permalink
-  route_name: comment.permalink
   title: 'View comment'
   tab_root_id: comment.permalink_tab
 comment.edit_page_tab:
+  route_name: comment_edit_page
-  route_name: comment.edit_page
   title: 'Edit'
   tab_root_id: comment.permalink_tab
   weight: 0
 comment.confirm_delete_tab:
+  route_name: comment_confirm_delete
-  route_name: comment.confirm_delete
   title: 'Delete'
   tab_root_id: comment.permalink_tab
   weight: 10
reverted:
--- b/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
+++ a/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
@@ -72,6 +72,12 @@
     foreach ($language_switcher->ul->li as $link) {
       $classes = explode(" ", (string) $link['class']);
       list($langcode) = array_intersect($classes, array('en', 'fr'));
+      if (in_array('active', $classes)) {
+        $links['active'][] = $langcode;
+      }
+      else {
+        $links['inactive'][] = $langcode;
+      }
       $anchor_classes = explode(" ", (string) $link->a['class']);
       if (in_array('active', $anchor_classes)) {
         $anchors['active'][] = $langcode;
@@ -80,6 +86,7 @@
         $anchors['inactive'][] = $langcode;
       }
     }
+    $this->assertIdentical($links, array('active' => array('en'), 'inactive' => array('fr')), 'Only the current language list item is marked as active on the language switcher block.');
     $this->assertIdentical($anchors, array('active' => array('en'), 'inactive' => array('fr')), 'Only the current language anchor is marked as active on the language switcher block.');
   }
 
diff -u b/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php
@@ -13,6 +13,14 @@
  * Tests for common theme functions.
  */
 class FunctionsTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('router_test');
+
   public static function getInfo() {
     return array(
       'name' => 'Theme functions',
@@ -158,13 +166,19 @@
         'title' => 'Front page',
         'href' => '<front>',
       ),
+      'router-test' => array(
+        'title' => 'Test route',
+        'route_name' => 'router_test.1',
+        'route_parameters' => array(),
+      ),
     );
 
     $expected_links = '';
     $expected_links .= '<ul id="somelinks">';
     $expected_links .= '<li class="a-link odd first"><a href="' . url('a/link') . '">' . check_plain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text even">' . check_plain('Plain "text"') . '</li>';
-    $expected_links .= '<li class="front-page odd last"><a href="' . url('<front>') . '" class="active">' . check_plain('Front page') . '</a></li>';
+    $expected_links .= '<li class="front-page odd last active"><a href="' . url('<front>') . '" class="active">' . check_plain('Front page') . '</a></li>';
+    $expected_links .= '<li class="router-test even last"><a href="' . \Drupal::urlGenerator()->generate('router_test.1') . '">' . check_plain('Test route') . '</a></li>';
     $expected_links .= '</ul>';
 
     // Verify that passing a string as heading works.
@@ -197,6 +211,7 @@
     $expected_links .= '<li class="a-link odd first"><a href="' . url('a/link') . '" class="a/class">' . check_plain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text even"><span class="a/class">' . check_plain('Plain "text"') . '</span></li>';
     $expected_links .= '<li class="front-page odd last"><a href="' . url('<front>') . '" class="active">' . check_plain('Front page') . '</a></li>';
+    $expected_links .= '<li class="router-test even last"><a href="' . \Drupal::urlGenerator()->generate('router_test.1') . '">' . check_plain('Test route') . '</a></li>';
     $expected_links .= '</ul>';
     $expected = $expected_heading . $expected_links;
     $this->assertThemeOutput('links', $variables, $expected);
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Utility/LinkGenerator.php
+++ b/core/lib/Drupal/Core/Utility/LinkGenerator.php
@@ -119,10 +119,7 @@ public function generate($text, $route_name, array $parameters = array(), array
     // URL path and query string as the current page. Note that this may be
     // removed from l() in https://drupal.org/node/1979468 and would be removed
     // or altered here also.
-    $variables['url_is_active'] = $route_name == $this->active['route_name']
-      // The language of an active link is equal to the current language.
-      && (empty($variables['options']['language']) || $variables['options']['language']->id == $this->active['language'])
-      && $full_parameters == $this->active['parameters'];
+    $variables['url_is_active'] = $this->isRouteActive($route_name, $full_parameters, $variables);
 
     // Add the "active" class if appropriate.
     if ($variables['url_is_active']) {
@@ -152,4 +149,16 @@ public function generate($text, $route_name, array $parameters = array(), array
     return '<a href="' . $url . '"' . $attributes . '>' . $text . '</a>';
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isRouteActive($route_name, array $route_parameters, array $variables) {
+    $url_is_active = $route_name == $this->active['route_name']
+      // The language of an active link is equal to the current language.
+      && (empty($variables['options']['language']) || $variables['options']['language']->id == $this->active['language'])
+      && $route_parameters == $this->active['parameters'];
+
+    return $url_is_active;
+  }
+
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Utility/LinkGeneratorInterface.php
+++ b/core/lib/Drupal/Core/Utility/LinkGeneratorInterface.php
@@ -71,4 +71,19 @@
    */
   public function generate($text, $route_name, array $parameters = array(), array $options = array());
 
+  /**
+   * Determines whether a given route is the current active route.
+   *
+   * @param string $route_name
+   *   The route name to check whether it is the current active one.
+   * @param array $route_parameters
+   *   The route parameters belonging to $route_name to check.
+   * @param array $variables
+   *   A link variables array containing the link options.
+   *
+   * @return bool
+   *   Returns TRUE if the route matches the current route, otherwise FALSE.
+   */
+  public function isRouteActive($route_name, array $route_parameters, array $variables);
+
 }
only in patch2:
unchanged:
--- a/core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php
@@ -333,6 +333,7 @@ public function testGenerateActive() {
     $request = new Request(array(), array(), array('system_path' => 'test-route-2'));
     $this->linkGenerator->setRequest($request);
     $result = $this->linkGenerator->generate('Test', 'test_route_1');
+    $this->assertFalse($this->linkGenerator->isRouteActive('test_route_1', array(), array()));
     $this->assertNotTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),
@@ -346,6 +347,7 @@ public function testGenerateActive() {
     $request->attributes->set('_raw_variables', $raw_variables);
     $this->linkGenerator->setRequest($request);
     $result = $this->linkGenerator->generate('Test', 'test_route_1');
+    $this->assertTrue($this->linkGenerator->isRouteActive('test_route_1', array(), array()));
     $this->assertTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),
@@ -353,6 +355,7 @@ public function testGenerateActive() {
 
     // Render a link with the same path and language as the current path.
     $result = $this->linkGenerator->generate('Test', 'test_route_1');
+    $this->assertTrue($this->linkGenerator->isRouteActive('test_route_1', array(), array()));
     $this->assertTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),
@@ -366,6 +369,7 @@ public function testGenerateActive() {
       array(),
       array('language' => new Language(array('id' => 'de')))
     );
+    $this->assertFalse($this->linkGenerator->isRouteActive('test_route_1', array(), array('options' => array('language' => new Language(array('id' => 'de'))))));
     $this->assertNotTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),
@@ -382,6 +386,7 @@ public function testGenerateActive() {
       array(),
       array('query' => array('value' => 'example_1')
     ));
+    $this->assertTrue($this->linkGenerator->isRouteActive('test_route_3', array('value' => 'example_1'), array()));
     $this->assertTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),
@@ -395,6 +400,7 @@ public function testGenerateActive() {
       array(),
       array('query' => array('value' => 'example_2'))
     );
+    $this->assertFalse($this->linkGenerator->isRouteActive('test_route_3', array('value' => 'example_2'), array()));
     $this->assertNotTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),
@@ -410,6 +416,7 @@ public function testGenerateActive() {
       array('object' => '1'),
       array('query' => array('value' => 'example_1'))
     );
+    $this->assertTrue($this->linkGenerator->isRouteActive('test_route_4', array('object' => '1', 'value' => 'example_1'), array()));
     $this->assertTag(array(
       'tag' => 'a',
       'attributes' => array('class' => 'active'),