diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index e64bfca..f48883c 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -1392,23 +1392,24 @@ function drupal_unpack($obj, $field = 'data') {
 /**
  * Translates a string to the current language or to a given language.
  *
- * The t() function serves two purposes. First, at run-time it translates
- * user-visible text into the appropriate language. Second, various mechanisms
- * that figure out what text needs to be translated work off t() -- the text
- * inside t() calls is added to the database of strings to be translated.
- * These strings are expected to be in English, so the first argument should
- * always be in English. To enable a fully-translatable site, it is important
- * that all human-readable text that will be displayed on the site or sent to
- * a user is passed through the t() function, or a related function. See the
- * @link http://drupal.org/node/322729 Localization API @endlink pages for
- * more information, including recommendations on how to break up or not
- * break up strings for translation.
- *
- * You should never use t() to translate variables, such as calling
- * @code t($text); @endcode, unless the text that the variable holds has been
- * passed through t() elsewhere (e.g., $text is one of several translated
- * literal strings in an array). It is especially important never to call
- * @code t($user_text); @endcode, where $user_text is some text that a user
+ * The t() function serves three purposes. First, at run-time it translates
+ * user-visible text into the appropriate language. Second, also at run-time it
+ * picks the correct language version of translateable configuration. Third,
+ * various mechanisms that figure out what text needs to be translated work
+ * off t() -- the text inside t() calls is added to the database of strings
+ * to be translated. These strings are expected to be in English, so the first
+ * argument should always be in English. To enable a fully-translatable site,
+ * it is important that all human-readable text that will be displayed on the
+ * site or sent to a user is passed through the t() function, or a related
+ * function. See the @link http://drupal.org/node/322729 Localization API
+ * @endlink pages for more information, including recommendations on how to
+ * break up or not break up strings for translation.
+ *
+ * You should never use t() to translate variables except config objects, such
+ * as calling @code t($text); @endcode, unless the text that the variable holds
+ * has been passed through t() elsewhere (e.g., $text is one of several
+ * translated literal strings in an array). It is especially important never to
+ * call @code t($user_text); @endcode, where $user_text is some text that a user
  * entered - doing that can lead to cross-site scripting and other security
  * problems. However, you can use variable substitution in your string, to put
  * variable text such as user names or link URLs into translated text. Variable
@@ -1426,8 +1427,10 @@ function drupal_unpack($obj, $field = 'data') {
  * available to code that needs localization. See st() and get_t() for
  * alternatives.
  *
- * @param $string
- *   A string containing the English string to translate.
+ * @param $input
+ *   A string containing the English string to translate or a translated
+ *   config array. To create a translated config pass in a langcode as a
+ *   subkey to Drupal\Core\Config\DrupalConfig::set().
  * @param $args
  *   An associative array of replacements to make after translation. Based
  *   on the first character of the key, the value is escaped and/or themed.
@@ -1447,13 +1450,24 @@ function drupal_unpack($obj, $field = 'data') {
  * @see format_string()
  * @ingroup sanitization
  */
-function t($string, array $args = array(), array $options = array()) {
+function t($input, array $args = array(), array $options = array()) {
   static $custom_strings;
 
   // Merge in default.
   if (empty($options['langcode'])) {
     $options['langcode'] = drupal_container()->get(LANGUAGE_TYPE_INTERFACE)->langcode;
   }
+  if (is_array($input)) {
+    if (isset($input[$options['langcode']])) {
+      return $input[$options['langcode']];
+    }
+    elseif (isset($input['_default'])) {
+      return $input[$input['_default']];
+    }
+    else {
+      return $input['en'];
+    }
+  }
   if (empty($options['context'])) {
     $options['context'] = '';
   }
@@ -1466,18 +1480,18 @@ function t($string, array $args = array(), array $options = array()) {
     $custom_strings[$options['langcode']] = variable_get('locale_custom_strings_' . $options['langcode'], array());
   }
   // Custom strings work for English too, even if locale module is disabled.
-  if (isset($custom_strings[$options['langcode']][$options['context']][$string])) {
-    $string = $custom_strings[$options['langcode']][$options['context']][$string];
+  if (isset($custom_strings[$options['langcode']][$options['context']][$input])) {
+    $input = $custom_strings[$options['langcode']][$options['context']][$input];
   }
   // Translate with locale module if enabled.
   elseif ($options['langcode'] != LANGUAGE_SYSTEM && ($options['langcode'] != 'en' || variable_get('locale_translate_english', FALSE)) && function_exists('locale')) {
-    $string = locale($string, $options['context'], $options['langcode']);
+    $input = locale($input, $options['context'], $options['langcode']);
   }
   if (empty($args)) {
-    return $string;
+    return $input;
   }
   else {
-    return format_string($string, $args);
+    return format_string($input, $args);
   }
 }
 
diff --git a/core/includes/install.inc b/core/includes/install.inc
index 1ebfb21..6d57f42 100644
--- a/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -711,7 +711,7 @@ function drupal_requirements_url($severity) {
  * @see get_t()
  * @ingroup sanitization
  */
-function st($string, array $args = array(), array $options = array()) {
+function st($input, array $args = array(), array $options = array()) {
   static $strings = NULL;
   global $install_state;
 
@@ -754,7 +754,7 @@ function st($string, array $args = array(), array $options = array()) {
       case '!':
     }
   }
-  return strtr((!empty($strings[$options['context']][$string]) ? $strings[$options['context']][$string] : $string), $args);
+  return strtr((!empty($strings[$options['context']][$input]) ? $strings[$options['context']][$input] : $input), $args);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Config/DrupalConfig.php b/core/lib/Drupal/Core/Config/DrupalConfig.php
index f5a9220..dee4cf5 100644
--- a/core/lib/Drupal/Core/Config/DrupalConfig.php
+++ b/core/lib/Drupal/Core/Config/DrupalConfig.php
@@ -129,16 +129,28 @@ class DrupalConfig {
    *
    * @param $key
    *   @todo
+   * @param $subkey
+   *   Typically a langcode but can be anything. After using a langcode here,
+   *   you can pass the result value of the corresponding get() call to t()
+   *   to get the version in the current language.
    * @param $value
    *   @todo
    */
-  public function set($key, $value) {
+  public function set($key, $value, $subkey = '') {
     // Type-cast value into a string.
     $value = $this->castValue($value);
 
     // The dot/period is a reserved character; it may appear between keys, but
     // not within keys.
     $parts = explode('.', $key);
+    if ($subkey) {
+      $default = $parts;
+      $default[] = '_default';
+      if (!drupal_array_get_nested_value($this->data, $default)) {
+        drupal_array_set_nested_value($this->data, $default, $subkey);
+      }
+      $parts[] = $subkey;
+    }
     if (count($parts) == 1) {
       $this->data[$key] = $value;
     }