diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 30a63e5..5a46c8c 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1,6 +1,6 @@
 <?php
 
-use Drupal\Component\Utility\Browser;
+use Drupal\Component\Utility\UserAgent;
 use Drupal\Component\Utility\Crypt;
 
 use Drupal\Component\Utility\Settings;
@@ -1607,7 +1607,7 @@ function install_select_language_form($form, &$form_state, $files = array()) {
   }
 
   $request = Request::createFromGlobals();
-  $browser_langcode = Browser::getLangcode($request->server->get('HTTP_ACCEPT_LANGUAGE'), $browser_options);
+  $browser_langcode = UserAgent::getBestMatchingLangcode($request->server->get('HTTP_ACCEPT_LANGUAGE'), $browser_options);
   $form['langcode'] = array(
     '#type' => 'select',
     '#title' => t('Choose language'),
diff --git a/core/lib/Drupal/Component/Utility/Browser.php b/core/lib/Drupal/Component/Utility/UserAgent.php
similarity index 71%
rename from core/lib/Drupal/Component/Utility/Browser.php
rename to core/lib/Drupal/Component/Utility/UserAgent.php
index 7977b39..361b057 100644
--- a/core/lib/Drupal/Component/Utility/Browser.php
+++ b/core/lib/Drupal/Component/Utility/UserAgent.php
@@ -2,58 +2,58 @@
 
 /**
  * @file
- * Contains \Drupal\Component\Utility\Browser.
+ * Contains \Drupal\Component\Utility\UserAgent.
  */
 
 namespace Drupal\Component\Utility;
 
 /**
- * Provides Browser-related utility functions.
+ * Provides user agent related utility functions.
  */
-class Browser {
+class UserAgent {
 
   /**
-   * Identifies browser language from the Accept-language HTTP header.
+   * Identifies user agent language from the Accept-language HTTP header.
    *
    * The algorithm works as follows:
-   * - map browser language codes to available language codes.
-   * - order all browser language codes by qvalue from high to low.
-   * - add generic browser language codes if they aren't already specified
+   * - map user agent language codes to available language codes.
+   * - order all user agent language codes by qvalue from high to low.
+   * - add generic user agent language codes if they aren't already specified
    *   but with a slightly lower qvalue.
    * - find the most specific available language code with the highest qvalue.
    * - if 2 or more languages are having the same qvalue, respect the order of
    *   them inside the $languages array.
    *
-   * We perform browser accept-language parsing only if page cache is disabled,
-   * otherwise we would cache a user-specific preference.
+   * We perform user agent accept-language parsing only if page cache is
+   * disabled, otherwise we would cache a user-specific preference.
    *
    * @param string $http_accept_language
    *   The value of the "Accept-Language" HTTP header.
    * @param array $langcodes
    *   An array of available language codes to pick from.
    * @param array $mappings
-   *   (optional) Custom mappings to support browsers that are sending non
+   *   (optional) Custom mappings to support user agents that are sending non
    *   standard language codes. No mapping is assumed by default.
    *
    * @return string
    *   The selected language code or FALSE if no valid language can be
    *   identified.
    */
-  public static function getLangcode($http_accept_language, $langcodes, $mappings = array()) {
+  public static function getBestMatchingLangcode($http_accept_language, $langcodes, $mappings = array()) {
     // The Accept-Language header contains information about the language
-    // preferences configured in the user's browser / operating system. RFC 2616
-    // (section 14.4) defines the Accept-Language header as follows:
+    // preferences configured in the user's user agent / operating system.
+    // RFC 2616 (section 14.4) defines the Accept-Language header as follows:
     //   Accept-Language = "Accept-Language" ":"
     //                  1#( language-range [ ";" "q" "=" qvalue ] )
     //   language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
     // Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
-    $browser_langcodes = array();
+    $ua_langcodes = array();
     if (preg_match_all('@(?<=[, ]|^)([a-zA-Z-]+|\*)(?:;q=([0-9.]+))?(?:$|\s*,\s*)@', trim($http_accept_language), $matches, PREG_SET_ORDER)) {
       foreach ($matches as $match) {
         if ($mappings) {
           $langcode = strtolower($match[1]);
-          foreach ($mappings as $browser_langcode => $standard_langcode) {
-            if ($langcode == $browser_langcode) {
+          foreach ($mappings as $ua_langcode => $standard_langcode) {
+            if ($langcode == $ua_langcode) {
               $match[1] = $standard_langcode;
             }
           }
@@ -67,9 +67,9 @@ public static function getLangcode($http_accept_language, $langcodes, $mappings
         // Take the highest qvalue for this langcode. Although the request
         // supposedly contains unique langcodes, our mapping possibly resolves
         // to the same langcode for different qvalues. Keep the highest.
-        $browser_langcodes[$langcode] = max(
+        $ua_langcodes[$langcode] = max(
           (int) ($qvalue * 1000),
-          (isset($browser_langcodes[$langcode]) ? $browser_langcodes[$langcode] : 0)
+          (isset($ua_langcodes[$langcode]) ? $ua_langcodes[$langcode] : 0)
         );
       }
     }
@@ -82,8 +82,8 @@ public static function getLangcode($http_accept_language, $langcodes, $mappings
     // possible.
     // See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4 and
     // http://blogs.msdn.com/b/ie/archive/2006/10/17/accept-language-header-for-internet-explorer-7.aspx
-    asort($browser_langcodes);
-    foreach ($browser_langcodes as $langcode => $qvalue) {
+    asort($ua_langcodes);
+    foreach ($ua_langcodes as $langcode => $qvalue) {
       // For Chinese languages the generic tag is either zh-hans or zh-hant, so
       // we need to handle this separately, we can not split $langcode on the
       // first occurrence of '-' otherwise we get a non-existing language zh.
@@ -96,11 +96,11 @@ public static function getLangcode($http_accept_language, $langcodes, $mappings
       else {
         $generic_tag = strtok($langcode, '-');
       }
-      if (!empty($generic_tag) && !isset($browser_langcodes[$generic_tag])) {
+      if (!empty($generic_tag) && !isset($ua_langcodes[$generic_tag])) {
         // Add the generic langcode, but make sure it has a lower qvalue as the
         // more specific one, so the more specific one gets selected if it's
-        // defined by both the browser and us.
-        $browser_langcodes[$generic_tag] = $qvalue - 0.1;
+        // defined by both the user agent and us.
+        $ua_langcodes[$generic_tag] = $qvalue - 0.1;
       }
     }
 
@@ -115,14 +115,15 @@ public static function getLangcode($http_accept_language, $langcodes, $mappings
 
       // If nothing matches below, the default qvalue is the one of the wildcard
       // language, if set, or is 0 (which will never match).
-      $qvalue = isset($browser_langcodes['*']) ? $browser_langcodes['*'] : 0;
+      $qvalue = isset($ua_langcodes['*']) ? $ua_langcodes['*'] : 0;
 
-      // Find the longest possible prefix of the browser-supplied language ('the
-      // language-range') that matches this site language ('the language tag').
+      // Find the longest possible prefix of the user agent supplied language
+      // ('the language-range') that matches this site language ('the language
+      // tag').
       $prefix = $langcode;
       do {
-        if (isset($browser_langcodes[$prefix])) {
-          $qvalue = $browser_langcodes[$prefix];
+        if (isset($ua_langcodes[$prefix])) {
+          $qvalue = $ua_langcodes[$prefix];
           break;
         }
       }
diff --git a/core/modules/language/lib/Drupal/language/ConfigurableLanguageManager.php b/core/modules/language/lib/Drupal/language/ConfigurableLanguageManager.php
index 3f4d09a..49c7ea4 100644
--- a/core/modules/language/lib/Drupal/language/ConfigurableLanguageManager.php
+++ b/core/modules/language/lib/Drupal/language/ConfigurableLanguageManager.php
@@ -172,14 +172,6 @@ public function getDefinedLanguageTypesInfo() {
   }
 
   /**
-   * {@inheritdoc}
-   */
-  function disableLanguageTypes(array $types) {
-    $this->languageTypes['configurable'] = array_diff($this->getLanguageTypes(), $types);
-    $this->saveLanguageTypesConfiguration($this->languageTypes);
-  }
-
-  /**
    * Stores language types configuration.
    */
   public function saveLanguageTypesConfiguration(array $config) {
@@ -254,7 +246,8 @@ public function getNegotiator() {
    */
   public function setNegotiator(LanguageNegotiatorInterface $negotiator) {
     $this->negotiator = $negotiator;
-    $this->reset();
+    $this->initialized = FALSE;
+    $this->negotiatedLanguages = array();
   }
 
   /**
diff --git a/core/modules/language/lib/Drupal/language/ConfigurableLanguageManagerInterface.php b/core/modules/language/lib/Drupal/language/ConfigurableLanguageManagerInterface.php
index a0c8206..c9a13d6 100644
--- a/core/modules/language/lib/Drupal/language/ConfigurableLanguageManagerInterface.php
+++ b/core/modules/language/lib/Drupal/language/ConfigurableLanguageManagerInterface.php
@@ -64,14 +64,6 @@ public function getDefinedLanguageTypes();
   public function getDefinedLanguageTypesInfo();
 
   /**
-   * Disables the given language types.
-   *
-   * @param array $types
-   *   An array of language type names.
-   */
-  function disableLanguageTypes(array $types);
-
-  /**
    * Stores language types configuration.
    *
    * @param array
diff --git a/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php b/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php
index 2976620..c9551f4 100644
--- a/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php
+++ b/core/modules/language/lib/Drupal/language/EventSubscriber/LanguageRequestSubscriber.php
@@ -78,12 +78,13 @@ public function __construct(ConfigurableLanguageManagerInterface $language_manag
   public function onKernelRequestLanguage(GetResponseEvent $event) {
     if ($event->getRequestType() == HttpKernelInterface::MASTER_REQUEST) {
       $request = $event->getRequest();
-      $this->negotiator->setContext($this->currentUser, $request);
-      $this->languageManager->setNegotiator($this->negotiator);
+      $this->negotiator->setCurrentUser($this->currentUser);
+      $this->negotiator->setRequest($request);
       if ($this->languageManager instanceof ConfigurableLanguageManagerInterface) {
+        $this->languageManager->setNegotiator($this->negotiator);
+        $this->languageManager->setRequest($request);
         $this->languageManager->initConfigOverrides();
       }
-      $this->languageManager->setRequest($request);
       // After the language manager has initialized, set the default langcode
       // for the string translations.
       $langcode = $this->languageManager->getCurrentLanguage()->id;
diff --git a/core/modules/language/lib/Drupal/language/Form/NegotiationConfigureForm.php b/core/modules/language/lib/Drupal/language/Form/NegotiationConfigureForm.php
index 6e0e266..c5b2a66 100644
--- a/core/modules/language/lib/Drupal/language/Form/NegotiationConfigureForm.php
+++ b/core/modules/language/lib/Drupal/language/Form/NegotiationConfigureForm.php
@@ -269,10 +269,10 @@ protected function configureFormTable(array &$form, $type)  {
         $table_form['description'][$method_id] = array('#markup' => Xss::filterAdmin($method['description']));
 
         $config_op = array();
-        if (isset($method['config'])) {
+        if (isset($method['config_path'])) {
           $config_op['configure'] = array(
             'title' => $this->t('Configure'),
-            'href' => $method['config'],
+            'href' => $method['config_path'],
           );
           // If there is at least one operation enabled show the operation
           // column.
diff --git a/core/modules/language/lib/Drupal/language/HttpKernel/PathProcessorLanguage.php b/core/modules/language/lib/Drupal/language/HttpKernel/PathProcessorLanguage.php
index 0a9137a..71a5cfe 100644
--- a/core/modules/language/lib/Drupal/language/HttpKernel/PathProcessorLanguage.php
+++ b/core/modules/language/lib/Drupal/language/HttpKernel/PathProcessorLanguage.php
@@ -51,13 +51,6 @@ class PathProcessorLanguage implements InboundPathProcessorInterface, OutboundPa
   protected $negotiator;
 
   /**
-   * The current active user.
-   *
-   * @return \Drupal\Core\Session\AccountInterface
-   */
-  protected $currentUser;
-
-  /**
    * Local cache for language path processors.
    *
    * @var array
@@ -90,7 +83,7 @@ public function __construct(ConfigFactory $config, Settings $settings, Configura
     $this->mixedModeSessions = $settings->get('mixed_mode_sessions', FALSE);
     $this->languageManager = $language_manager;
     $this->negotiator = $negotiator;
-    $this->currentUser = $current_user;
+    $this->negotiator->setCurrentUser($current_user);
   }
 
   /**
@@ -117,7 +110,7 @@ public function processOutbound($path, &$options = array(), Request $request = N
       $this->multilingual = $this->languageManager->isMultilingual();
     }
     if ($this->multilingual) {
-      $this->negotiator->setContext($this->currentUser, $request);
+      $this->negotiator->setRequest($request);
       $scope = 'outbound';
       if (!isset($this->processors[$scope])) {
         $this->initProcessors($scope);
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
index 2f2b5cf..5dc497b 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodBase.php
@@ -8,6 +8,7 @@
 namespace Drupal\language;
 
 use Drupal\Core\Config\ConfigFactory;
+use Drupal\Core\Language\Language;
 use Drupal\Core\Session\AccountInterface;
 
 /**
@@ -57,4 +58,12 @@ public function setCurrentUser(AccountInterface $current_user) {
     $this->currentUser = $current_user;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function persist(Language $language) {
+    // Remember the method ID used to detect the language.
+    $language->method_id = static::METHOD_ID;
+  }
+
 }
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodInterface.php b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodInterface.php
index cd19bb1..eb23977 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodInterface.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiationMethodInterface.php
@@ -8,6 +8,7 @@
 namespace Drupal\language;
 
 use Drupal\Core\Config\ConfigFactory;
+use Drupal\Core\Language\Language;
 use Drupal\Core\Session\AccountInterface;
 use Symfony\Component\HttpFoundation\Request;
 
@@ -53,4 +54,11 @@ public function setCurrentUser(AccountInterface $current_user);
    */
   public function getLangcode(Request $request = NULL);
 
+  /**
+   * Notifies the plugin that the language code it returned has been accepted.
+   *
+   * @param string $langcode
+   */
+  public function persist(Language $language);
+
 }
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiator.php b/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
index 855c8aa..f2a74f6 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiator.php
@@ -116,8 +116,15 @@ public function reset() {
   /**
    * {@inheritdoc}
    */
-  public function setContext(AccountInterface $current_user, Request $request) {
+  public function setCurrentUser(AccountInterface $current_user) {
     $this->currentUser = $current_user;
+    $this->reset();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setRequest(Request $request) {
     $this->request = $request;
     $this->reset();
   }
@@ -126,7 +133,7 @@ public function setContext(AccountInterface $current_user, Request $request) {
    * {@inheritdoc}
    */
   public function initializeType($type) {
-    $language = FALSE;
+    $language = NULL;
 
     if ($this->currentUser && $this->request) {
       // Execute the language negotiation methods in the order they were set up
@@ -140,11 +147,10 @@ public function initializeType($type) {
         // the language negotiation method cache from being unintentionally
         // altered. The same methods might be used with different language types
         // based on configuration.
-        $language = !empty($this->negotiatedLanguages[$method_id]) ? clone($this->negotiatedLanguages[$method_id]) : FALSE;
+        $language = !empty($this->negotiatedLanguages[$method_id]) ? clone($this->negotiatedLanguages[$method_id]) : NULL;
 
         if ($language) {
-          // Remember the method ID used to detect the language.
-          $language->method_id = $method_id;
+          $this->getNegotiationMethodInstance($method_id)->persist($language);
           break;
         }
       }
@@ -178,11 +184,11 @@ protected function getConfiguration($type) {
    *   The string identifier of the language negotiation method to use to detect
    *   language.
    *
-   * @return \Drupal\Core\Language\Language|FALSE
+   * @return \Drupal\Core\Language\Language|NULL
    *   Negotiated language object for given type and method, FALSE otherwise.
    */
   protected function negotiateLanguage($type, $method_id) {
-    $langcode = FALSE;
+    $langcode = NULL;
     $method = $this->negotiatorManager->getDefinition($method_id);
 
     if (!isset($method['types']) || in_array($type, $method['types'])) {
@@ -203,7 +209,7 @@ protected function negotiateLanguage($type, $method_id) {
     }
 
     $languages = $this->languageManager->getLanguages();
-    return isset($languages[$langcode]) ? $languages[$langcode] : FALSE;
+    return isset($languages[$langcode]) ? $languages[$langcode] : NULL;
   }
 
   /**
diff --git a/core/modules/language/lib/Drupal/language/LanguageNegotiatorInterface.php b/core/modules/language/lib/Drupal/language/LanguageNegotiatorInterface.php
index f16ed54..0654fde 100644
--- a/core/modules/language/lib/Drupal/language/LanguageNegotiatorInterface.php
+++ b/core/modules/language/lib/Drupal/language/LanguageNegotiatorInterface.php
@@ -116,14 +116,20 @@
   public function reset();
 
   /**
-   * Sets the contextual data and resets all language types.
+   * Sets the current active user and resets all language types.
    *
    * @param \Drupal\Core\Session\AccountInterface $current_user
    *   The current active user.
+   */
+  public function setCurrentUser(AccountInterface $current_user);
+
+  /**
+   * Sets the active request and resets all language types.
+   *
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The HttpRequest object representing the current request.
    */
-  public function setContext(AccountInterface $current_user, Request $request);
+  public function setRequest(Request $request);
 
   /**
    * Initializes the specified language type.
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationBrowser.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationBrowser.php
index 85d49c5..0ce2c86 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationBrowser.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationBrowser.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\language\Plugin\LanguageNegotiation;
 
-use Drupal\Component\Utility\Browser;
+use Drupal\Component\Utility\UserAgent;
 use Drupal\language\LanguageNegotiationMethodBase;
 use Symfony\Component\HttpFoundation\Request;
 
@@ -20,7 +20,7 @@
  *   cache = 0,
  *   name = @Translation("Browser"),
  *   description = @Translation("Language from the browser's language settings."),
- *   config = "admin/config/regional/language/detection/browser"
+ *   config_path = "admin/config/regional/language/detection/browser"
  * )
  */
 class LanguageNegotiationBrowser extends LanguageNegotiationMethodBase {
@@ -34,13 +34,13 @@ class LanguageNegotiationBrowser extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    $langcode = FALSE;
+    $langcode = NULL;
 
     if ($this->languageManager && $request && $request->server->get('HTTP_ACCEPT_LANGUAGE')) {
       $http_accept_language = $request->server->get('HTTP_ACCEPT_LANGUAGE');
       $langcodes = array_keys($this->languageManager->getLanguages());
       $mappings = $this->config->get('language.mappings')->get();
-      $langcode = Browser::getLangcode($http_accept_language, $langcodes, $mappings);
+      $langcode = UserAgent::getBestMatchingLangcode($http_accept_language, $langcodes, $mappings);
     }
 
     return $langcode;
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSelected.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSelected.php
index fba2a33..bdbedc5 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSelected.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSelected.php
@@ -18,7 +18,7 @@
  *   weight = 12,
  *   name = @Translation("Selected language"),
  *   description = @Translation("Language based on a selected language."),
- *   config = "admin/config/regional/language/detection/selected"
+ *   config_path = "admin/config/regional/language/detection/selected"
  * )
  */
 class LanguageNegotiationSelected extends LanguageNegotiationMethodBase {
@@ -32,14 +32,11 @@ class LanguageNegotiationSelected extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    $langcode = FALSE;
+    $langcode = NULL;
 
     if ($this->languageManager) {
       $languages = $this->languageManager->getLanguages();
       $langcode = $this->config->get('language.negotiation')->get('selected_langcode');
-      if (!isset($languages[$langcode])) {
-        $langcode = $this->languageManager->getDefaultLanguage()->id;
-      }
     }
 
     return $langcode;
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
index dd7e5b4..e56278d 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\language\Plugin\LanguageNegotiation;
 
+use Drupal\Core\Language\Language;
 use Drupal\Core\PathProcessor\OutboundPathProcessorInterface;
 use Drupal\language\LanguageNegotiationMethodBase;
 use Drupal\language\LanguageSwitcherInterface;
@@ -20,7 +21,7 @@
  *   weight = -6,
  *   name = @Translation("Session"),
  *   description = @Translation("Language from a request/session parameter."),
- *   config = "admin/config/regional/language/detection/session"
+ *   config_path = "admin/config/regional/language/detection/session"
  * )
  */
 class LanguageNegotiationSession extends LanguageNegotiationMethodBase implements OutboundPathProcessorInterface, LanguageSwitcherInterface {
@@ -57,23 +58,29 @@ class LanguageNegotiationSession extends LanguageNegotiationMethodBase implement
   public function getLangcode(Request $request = NULL) {
     $config = $this->config->get('language.negotiation')->get('session');
     $param = $config['parameter'];
-    $langcode = $request && $request->query->get($param) ? $request->query->get($param) : FALSE;
+    $langcode = $request && $request->query->get($param) ? $request->query->get($param) : NULL;
+    if (!$langcode && isset($_SESSION[$param])) {
+      $langcode = $_SESSION[$param];
+    }
+    return $langcode;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function persist(Language $language) {
+    parent::persist($language);
 
     // We need to update the session parameter with the request value only if we
     // have an authenticated user.
+    $langcode = $language->id;
     if ($langcode && $this->languageManager) {
       $languages = $this->languageManager->getLanguages();
       if ($this->currentUser->isAuthenticated() && isset($languages[$langcode])) {
-        $_SESSION[$param] = $langcode;
+        $config = $this->config->get('language.negotiation')->get('session');
+        $_SESSION[$config['parameter']] = $langcode;
       }
     }
-
-    // Session parameter.
-    if (isset($_SESSION[$param])) {
-      $langcode = $_SESSION[$param];
-    }
-
-    return $langcode;
   }
 
   /**
@@ -136,7 +143,7 @@ function getLanguageSwitchLinks(Request $request, $type, $path) {
         $links[$langcode]['query'][$param] = $langcode;
       }
       else {
-        $links[$langcode]['attributes']['class'][] = ' session-active';
+        $links[$langcode]['attributes']['class'][] = 'session-active';
       }
     }
 
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
index c3e5aeb..3b64974 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
@@ -32,7 +32,7 @@ class LanguageNegotiationUI extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    return $this->languageManager ? $this->languageManager->getCurrentLanguage()->id : FALSE;
+    return $this->languageManager ? $this->languageManager->getCurrentLanguage()->id : NULL;
   }
 
 }
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
index 7cb8bc7..a72ca44 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
@@ -23,7 +23,7 @@
  *   weight = -8,
  *   name = @Translation("URL"),
  *   description = @Translation("Language from the URL (Path prefix or domain)."),
- *   config = "admin/config/regional/language/detection/url"
+ *   config_path = "admin/config/regional/language/detection/url"
  * )
  */
 class LanguageNegotiationUrl extends LanguageNegotiationMethodBase implements InboundPathProcessorInterface, OutboundPathProcessorInterface, LanguageSwitcherInterface {
@@ -47,7 +47,7 @@ class LanguageNegotiationUrl extends LanguageNegotiationMethodBase implements In
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    $langcode = FALSE;
+    $langcode = NULL;
 
     if ($request && $this->languageManager) {
       $languages = $this->languageManager->getLanguages();
@@ -68,7 +68,7 @@ public function getLangcode(Request $request = NULL) {
             }
           }
 
-           if ($negotiated_language !== FALSE && $negotiated_language instanceof \Drupal\Core\Language\Language) {
+          if ($negotiated_language) {
             $langcode = $negotiated_language->id;
           }
           break;
@@ -133,7 +133,7 @@ public function processOutbound($path, &$options = array(), Request $request = N
       $options['language'] = $language_url;
     }
     // We allow only enabled languages here.
-    elseif (is_object($options['language']) && !isset($languages[$options['language']->id])) {
+    elseif (!is_object($options['language']) || !isset($languages[$options['language']->id])) {
       return $path;
     }
     $config = $this->config->get('language.negotiation')->get('url');
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
index 379cf79..2310153 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
+++ b/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
@@ -51,7 +51,7 @@ class LanguageNegotiationUrlFallback extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    $langcode = FALSE;
+    $langcode = NULL;
 
     if ($this->languageManager) {
       $default = $this->languageManager->getDefaultLanguage();
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
index f660eb8..5571668 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\language\Tests;
 
-use Drupal\Component\Utility\Browser;
+use Drupal\Component\Utility\UserAgent;
 use Drupal\Core\Language\Language;
 use Drupal\simpletest\WebTestBase;
 use Symfony\Component\HttpFoundation\Request;
@@ -157,7 +157,7 @@ function testLanguageFromBrowser() {
 
     $mappings = $this->container->get('config.factory')->get('language.mappings')->get();
     foreach ($test_cases as $accept_language => $expected_result) {
-      $result = Browser::getLangcode($accept_language, array_keys($languages), $mappings);
+      $result = UserAgent::getBestMatchingLangcode($accept_language, array_keys($languages), $mappings);
       $this->assertIdentical($result, $expected_result, format_string("Language selection '@accept-language' selects '@result', result = '@actual'", array('@accept-language' => $accept_language, '@result' => $expected_result, '@actual' => isset($result) ? $result : 'none')));
     }
   }
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php
index 9e3cdab..e8b3b26 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php
@@ -10,11 +10,12 @@
 use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationBrowser;
 use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationSelected;
 use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl;
-use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUser;
-use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin;
+use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUser;
+use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin;
 use Drupal\simpletest\WebTestBase;
 use Drupal\Core\Language\Language;
 use Symfony\Component\HttpFoundation\Request;
+use Drupal\language\LanguageNegotiatorInterface;
 
 /**
  * Test UI language negotiation
@@ -53,7 +54,7 @@ class LanguageUILanguageNegotiationTest extends WebTestBase {
    *
    * @var array
    */
-  public static $modules = array('locale', 'language_test', 'block');
+  public static $modules = array('locale', 'language_test', 'block', 'user');
 
   public static function getInfo() {
     return array(
@@ -165,7 +166,7 @@ function testUILanguageNegotiation() {
       'language_negotiation' => array(LanguageNegotiationSelected::METHOD_ID),
       'path' => 'admin/config',
       'expect' => $default_string,
-      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
       'http_header' => $http_header_browser_fallback,
       'message' => 'SELECTED > DEFAULT: UI language is switched based on selected language.',
     );
@@ -177,7 +178,7 @@ function testUILanguageNegotiation() {
       'language_negotiation' => array(LanguageNegotiationSelected::METHOD_ID),
       'path' => 'admin/config',
       'expect' => $default_string,
-      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
       'http_header' => $http_header_browser_fallback,
       'message' => 'SELECTED > DEFAULT: UI language is switched based on selected language.',
     );
@@ -189,7 +190,7 @@ function testUILanguageNegotiation() {
         'language_negotiation' => array(LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationSelected::METHOD_ID),
         'path' => 'admin/config',
         'expect' => $default_string,
-        'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+        'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
         'http_header' => $http_header_browser_fallback,
         'message' => 'URL (PATH) > DEFAULT: no language prefix, UI language is default and the browser language preference setting is not used.',
       ),
@@ -225,7 +226,7 @@ function testUILanguageNegotiation() {
         'language_negotiation' => array(LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationBrowser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID),
         'path' => 'admin/config',
         'expect' => $default_string,
-        'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+        'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
         'http_header' => $http_header_blah,
         'message' => 'URL (PATH) > BROWSER > DEFAULT: no language prefix and browser language preference set to unknown language should use default language',
       ),
@@ -250,7 +251,7 @@ function testUILanguageNegotiation() {
       'language_negotiation' => array(LanguageNegotiationUser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID),
       'path' => 'admin/config',
       'expect' => $default_string,
-      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
       'http_header' => array(),
       'message' => 'USER > DEFAULT: no preferred user language setting, the UI language is default',
     );
@@ -265,7 +266,7 @@ function testUILanguageNegotiation() {
       'language_negotiation' => array(LanguageNegotiationUser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID),
       'path' => 'admin/config',
       'expect' => $default_string,
-      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
       'http_header' => array(),
       'message' => 'USER > DEFAULT: invalid preferred user language setting, the UI language is default',
     );
@@ -293,7 +294,7 @@ function testUILanguageNegotiation() {
       'language_negotiation' => array(LanguageNegotiationUserAdmin::METHOD_ID, LanguageNegotiationSelected::METHOD_ID),
       'path' => 'admin/config',
       'expect' => $default_string,
-      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
       'http_header' => array(),
       'message' => 'USER ADMIN > DEFAULT: no preferred user admin language setting, the UI language is default',
     );
@@ -307,7 +308,7 @@ function testUILanguageNegotiation() {
       'language_negotiation' => array(LanguageNegotiationUserAdmin::METHOD_ID, LanguageNegotiationSelected::METHOD_ID),
       'path' => 'admin/config',
       'expect' => $default_string,
-      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
+      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
       'http_header' => array(),
       'message' => 'USER ADMIN > DEFAULT: invalid preferred user admin language setting, the UI language is default',
     );
diff --git a/core/modules/user/lib/Drupal/user/AccountFormController.php b/core/modules/user/lib/Drupal/user/AccountFormController.php
index 7c62df0..e67520b 100644
--- a/core/modules/user/lib/Drupal/user/AccountFormController.php
+++ b/core/modules/user/lib/Drupal/user/AccountFormController.php
@@ -12,8 +12,8 @@
 use Drupal\Core\Language\Language;
 use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\language\ConfigurableLanguageManagerInterface;
-use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin;
-use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUser;
+use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin;
+use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUser;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php b/core/modules/user/lib/Drupal/user/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
similarity index 88%
rename from core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
rename to core/modules/user/lib/Drupal/user/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
index 2e267e3..f2c99fe 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
+++ b/core/modules/user/lib/Drupal/user/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl.
  */
 
-namespace Drupal\language\Plugin\LanguageNegotiation;
+namespace Drupal\user\Plugin\LanguageNegotiation;
 
 use Drupal\language\LanguageNegotiationMethodBase;
 use Symfony\Component\HttpFoundation\Request;
@@ -14,7 +14,7 @@
  * Class for identifying language from the user preferences.
  *
  * @Plugin(
- *   id = \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUser::METHOD_ID,
+ *   id = \Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUser::METHOD_ID,
  *   weight = -4,
  *   name = @Translation("User"),
  *   description = @Translation("Follow the user's language preference.")
@@ -31,7 +31,7 @@ class LanguageNegotiationUser extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    $langcode = FALSE;
+    $langcode = NULL;
 
     // User preference (only for authenticated users).
     if ($this->languageManager && $this->currentUser->isAuthenticated()) {
diff --git a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php b/core/modules/user/lib/Drupal/user/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
similarity index 87%
rename from core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
rename to core/modules/user/lib/Drupal/user/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
index fd1639c..c7a42eb 100644
--- a/core/modules/language/lib/Drupal/language/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
+++ b/core/modules/user/lib/Drupal/user/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
@@ -2,10 +2,10 @@
 
 /**
  * @file
- * Contains \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin.
+ * Contains \Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin.
  */
 
-namespace Drupal\language\Plugin\LanguageNegotiation;
+namespace Drupal\user\Plugin\LanguageNegotiation;
 
 use Drupal\language\LanguageNegotiationMethodBase;
 use Symfony\Component\HttpFoundation\Request;
@@ -14,7 +14,7 @@
  * Identifies admin language from the user preferences.
  *
  * @Plugin(
- *   id = Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin::METHOD_ID,
+ *   id = Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin::METHOD_ID,
  *   types = {Drupal\Core\Language\Language::TYPE_INTERFACE},
  *   weight = 10,
  *   name = @Translation("Account administration pages"),
@@ -32,7 +32,7 @@ class LanguageNegotiationUserAdmin extends LanguageNegotiationMethodBase {
    * {@inheritdoc}
    */
   public function getLangcode(Request $request = NULL) {
-    $langcode = FALSE;
+    $langcode = NULL;
 
     // User preference (only for authenticated users).
     if ($this->languageManager && $this->currentUser->isAuthenticated() && $this->isAdminPath($request)) {