diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 5577be4..8cf8ad4 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -1487,8 +1487,6 @@ function bootstrap_hooks() {
  * @ingroup sanitization
  */
 function t($string, array $args = array(), array $options = array()) {
-  static $custom_strings;
-
   // Merge in default.
   if (empty($options['langcode'])) {
     $options['langcode'] = language(LANGUAGE_TYPE_INTERFACE)->langcode;
@@ -1497,21 +1495,10 @@ function t($string, array $args = array(), array $options = array()) {
     $options['context'] = '';
   }
 
-  // First, check for an array of customized strings. If present, use the array
-  // *instead of* database lookups. This is a high performance way to provide a
-  // handful of string replacements. See settings.php for examples.
-  // Cache the $custom_strings variable to improve performance.
-  if (!isset($custom_strings[$options['langcode']])) {
-    $custom_strings[$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];
-  }
-  // 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']);
-  }
+  $translation = drupal_container()->get('locale.translation')
+    ->translate($options['langcode'], $string, $options['context']);
+  $string = $translation === FALSE ? $string : $translation;
+
   if (empty($args)) {
     return $string;
   }
@@ -2480,6 +2467,14 @@ function drupal_container(Container $new_container = NULL, $rebuild = FALSE) {
 
     // Register the EntityManager.
     $container->register('plugin.manager.entity', 'Drupal\Core\Entity\EntityManager');
+
+    // Register a minimum translation service just in case a translation is
+    // attempted before language initialization.
+    $container
+      ->register('locale.translation.custom', 'Drupal\Core\Translation\CustomStrings');
+    $container
+      ->register('locale.translation', 'Drupal\Core\Translation\TranslationFallback')
+      ->addArgument(new Reference('locale.translation.custom'));
   }
   return $container;
 }
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 2b117bc..fe377ac 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -322,11 +322,23 @@ function install_begin_request(&$install_state) {
     $container->register('config.factory', 'Drupal\Core\Config\ConfigFactory')
       ->addArgument(new Reference('config.storage'))
       ->addArgument(new Reference('dispatcher'));
+    $container
+      ->register('locale.translation.custom', 'Drupal\Core\Translation\CustomStrings');
     drupal_container($container);
   }
 
   // Set up $language, so t() caller functions will still work.
   drupal_language_initialize();
+  // Set up file based translation as fall back for localization.
+  drupal_container()
+    ->register('locale.translation.file', 'Drupal\Core\Translation\FileTranslation')
+    ->addArgument(variable_get('locale_translate_file_directory', conf_path() . '/files/translations'));
+  drupal_container()
+     ->register('locale.translation.custom', 'Drupal\Core\Translation\CustomStrings');
+  drupal_container()
+    ->register('locale.translation', 'Drupal\Core\Translation\TranslationFallback')
+    ->addArgument(new Reference('locale.translation.custom'))
+    ->addArgument(new Reference('locale.translation.file'));
 
   require_once DRUPAL_ROOT . '/core/includes/ajax.inc';
   // Override the module list with a minimal set of modules.
@@ -1281,7 +1293,7 @@ function install_select_profile_form($form, &$form_state, $install_state) {
  * @see file_scan_directory()
  */
 function install_find_translations() {
-  $files = install_find_translation_files();
+  $files = drupal_container()->get('locale.translation.file')->findTranslationFiles();
   // English does not need a translation file.
   array_unshift($files, (object) array('name' => 'en'));
   foreach ($files as $key => $file) {
@@ -1297,26 +1309,6 @@ function install_find_translations() {
 }
 
 /**
- * Finds installer translations either for a specific langcode or all languages.
- *
- * @param $langcode
- *   (optional) The language code corresponding to the language for which we
- *   want to find translation files. If omitted, information on all available
- *   files will be returned.
- *
- * @return
- *   An associative array of file information objects keyed by file URIs as
- *   returned by file_scan_directory().
- *
- * @see file_scan_directory()
- */
-function install_find_translation_files($langcode = NULL) {
-  $directory = variable_get('locale_translate_file_directory', conf_path() . '/files/translations');
-  $files = file_scan_directory($directory, '!drupal-\d+\.\d+\.' . (!empty($langcode) ? preg_quote($langcode, '!') : '[^\.]+') . '\.po$!', array('recurse' => FALSE));
-  return $files;
-}
-
-/**
  * Selects which language to use during installation.
  *
  * @param $install_state
diff --git a/core/includes/install.inc b/core/includes/install.inc
index a2666ae..0be0305 100644
--- a/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -6,7 +6,7 @@
  */
 
 use Drupal\Core\Database\Database;
-use Drupal\locale\Gettext;
+use Drupal\Core\Translation\FileTranslation;
 
 /**
  * Requirement severity -- Informational message only.
@@ -740,53 +740,23 @@ function drupal_requirements_url($severity) {
  * Use st() if your code will only run during installation and never any other
  * time. Use get_t() if your code could run in either circumstance.
  *
+ * @todo Remove or keep as a t wrapper to mark config strings..?
+ *
  * @see t()
  * @see get_t()
  * @ingroup sanitization
  */
 function st($string, array $args = array(), array $options = array()) {
-  static $strings = NULL;
+  static $langcode;
   global $install_state;
 
-  if (empty($options['context'])) {
-    $options['context'] = '';
-  }
-
-  if (!isset($strings)) {
-    $strings = array();
-    if (isset($install_state['parameters']['langcode'])) {
-      // If the given langcode was selected, there should be at least one .po
-      // file with its name in the pattern drupal-$version.$langcode.po.
-      // This might or might not be the entire filename. It is also possible
-      // that multiple files end with the same suffix, even if unlikely.
-      $files = install_find_translation_files($install_state['parameters']['langcode']);
-      if (!empty($files)) {
-        // Register locale classes with the classloader. Locale module is not
-        // yet enabled at this stage, so this is not happening automatically.
-        drupal_classloader_register('locale', drupal_get_path('module', 'locale'));
-        $strings = Gettext::filesToArray($install_state['parameters']['langcode'], $files);
-      }
-    }
+  // If not set, initialize installation language if possible.
+  if (!isset($langcode) && isset($install_state['parameters']['langcode'])) {
+    $langcode = $install_state['parameters']['langcode'];
   }
+  $options += array('langcode' => $langcode);
 
-  require_once DRUPAL_ROOT . '/core/includes/theme.inc';
-  // Transform arguments before inserting them
-  foreach ($args as $key => $value) {
-    switch ($key[0]) {
-      // Escaped only
-      case '@':
-        $args[$key] = check_plain($value);
-        break;
-      // Escaped and placeholder
-      case '%':
-      default:
-        $args[$key] = '<em>' . check_plain($value) . '</em>';
-        break;
-      // Pass-through
-      case '!':
-    }
-  }
-  return strtr((!empty($strings[$options['context']][$string]) ? $strings[$options['context']][$string] : $string), $args);
+  return t($string, $args, $options);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Translation/CustomStrings.php b/core/lib/Drupal/Core/Translation/CustomStrings.php
new file mode 100644
index 0000000..e9fb81a
--- /dev/null
+++ b/core/lib/Drupal/Core/Translation/CustomStrings.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Language\CustomStrings.
+ */
+
+namespace Drupal\Core\Translation;
+
+/**
+ * String translator using overrides from variables.
+ *
+ * This is a high performance way to provide a handful of string replacements.
+ * See settings.php for examples.
+ */
+class CustomStrings extends StaticTranslation {
+
+  /**
+   * Overrides Drupal\Core\Language\StaticTranslation::loadLanguage().
+   */
+  protected function loadLanguage($langcode) {
+    return variable_get('locale_custom_strings_' . $langcode, array());
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Translation/FileTranslation.php b/core/lib/Drupal/Core/Translation/FileTranslation.php
new file mode 100644
index 0000000..255e068
--- /dev/null
+++ b/core/lib/Drupal/Core/Translation/FileTranslation.php
@@ -0,0 +1,104 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Translation\FileTranslation.
+ */
+
+namespace Drupal\Core\Translation;
+
+use Drupal\Component\Gettext\PoStreamReader;
+use Drupal\Component\Gettext\PoMemoryWriter;
+
+/**
+ * File based string translation.
+ *
+ * Translates a string when some systems are not available.
+ *
+ * Used during the install process, when database, theme, and localization
+ * system is possibly not yet available.
+ *
+ * Use t() if your code will never run during the Drupal installation phase.
+ * Use st() if your code will only run during installation and never any other
+ * time. Use get_t() if your code could run in either circumstance.
+ */
+class FileTranslation extends StaticTranslation {
+
+  /**
+   * Directory to find translation files in the file system.
+   *
+   * @var string
+   */
+  protected $directory;
+
+  /**
+   * Overrides Drupal\Core\Language\StaticTranslation::__construct().
+   */
+  public function __construct($directory) {
+    parent::__construct();
+    $this->directory = $directory;
+  }
+
+  /**
+   * Overrides Drupal\Core\Language\StaticTranslation::loadLanguage().
+   */
+  protected function loadLanguage($langcode) {
+    // If the given langcode was selected, there should be at least one .po
+    // file with its name in the pattern drupal-$version.$langcode.po.
+    // This might or might not be the entire filename. It is also possible
+    // that multiple files end with the same suffix, even if unlikely.
+    $files = $this->findTranslationFiles($langcode);
+
+    if (!empty($files)) {
+      return $this->filesToArray($langcode, $files);
+    }
+    else {
+      return array();
+    }
+  }
+
+  /**
+   * Finds installer translations either for a specific langcode or all languages.
+   *
+   * @param $langcode
+   *   (optional) The language code corresponding to the language for which we
+   *   want to find translation files. If omitted, information on all available
+   *   files will be returned.
+   *
+   * @return
+   *   An associative array of file information objects keyed by file URIs as
+   *   returned by file_scan_directory().
+   *
+   * @see file_scan_directory()
+   */
+  public function findTranslationFiles($langcode = NULL) {
+    $files = file_scan_directory($this->directory, '!drupal-\d+\.\d+\.' . (!empty($langcode) ? preg_quote($langcode, '!') : '[^\.]+') . '\.po$!', array('recurse' => FALSE));
+    return $files;
+  }
+
+  /**
+   * Reads the given Gettext PO files into a data structure.
+   *
+   * @param string $langcode
+   *   Language code string.
+   * @param array $files
+   *   List of file objects with URI properties pointing to read.
+   *
+   * @return array
+   *   Structured array as produced by a PoMemoryWriter.
+   *
+   * @see Drupal\Component\Gettext\PoMemoryWriter
+   */
+  public static function filesToArray($langcode, array $files) {
+    $writer = new PoMemoryWriter();
+    $writer->setLangcode($langcode);
+    foreach ($files as $file) {
+      $reader = new PoStreamReader();
+      $reader->setURI($file->uri);
+      $reader->setLangcode($langcode);
+      $reader->open();
+      $writer->writeItems($reader, -1);
+    }
+    return $writer->getData();
+  }
+}
diff --git a/core/lib/Drupal/Core/Translation/StaticTranslation.php b/core/lib/Drupal/Core/Translation/StaticTranslation.php
new file mode 100644
index 0000000..2b35b1b
--- /dev/null
+++ b/core/lib/Drupal/Core/Translation/StaticTranslation.php
@@ -0,0 +1,64 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Language\StaticTranslation.
+ */
+
+namespace Drupal\Core\Translation;
+
+/**
+ * String translator with a static cache for translations.
+ *
+ * This is a high performance way to provide a handful of string replacements.
+ */
+class StaticTranslation implements TranslationInterface {
+
+  /**
+   * String translations
+   *
+   * @var array
+   *   Array of cached translations indexed by language and context.
+   */
+  protected $translations;
+
+  /**
+   * Constructs a translator from an array of translations.
+   *
+   * @param array $translations
+   *   Array of override strings indexed by language and context
+   */
+  public function __construct($translations = array()) {
+    $this->translations = $translations;
+  }
+
+  /**
+   * Implements Drupal\Core\Language\TranslationInterface::translate()
+   */
+  public function translate($langcode, $string, $context) {
+    if (!isset($this->translations[$langcode])) {
+      $this->translations[$langcode] = $this->loadLanguage($langcode);
+    }
+    if (isset($this->translations[$langcode][$context][$string])) {
+      return $this->translations[$langcode][$context][$string];
+    }
+    else {
+      return FALSE;
+    }
+  }
+
+  /**
+   * Implements Drupal\Core\Language\TranslationInterface::reset()
+   */
+  public function reset() {
+    $this->translations = array();
+  }
+
+  /**
+   * Add translations for new language.
+   */
+  protected function loadLanguage($langcode) {
+    return array();
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Translation/TranslationFallback.php b/core/lib/Drupal/Core/Translation/TranslationFallback.php
new file mode 100644
index 0000000..0cad02e
--- /dev/null
+++ b/core/lib/Drupal/Core/Translation/TranslationFallback.php
@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Translation\TranslationFallback.
+ */
+
+namespace Drupal\Core\Translation;
+
+/**
+ * String translator with a fallback system.
+ */
+class TranslationFallback implements TranslationInterface {
+
+
+  /**
+   * Translation systems.
+   *
+   * @var array
+   *   Array of Drupal\Core\Language\TranslationInterface objects
+   */
+  protected $translators;
+
+
+  /**
+   * Constructs a translator from any number of translation systems.
+   *
+   * The order of the translators in the array will be the order in which they
+   * will be tried for a translation.
+   *
+   * @param $translator1, $translator2
+   *   Multiple containing Drupal\Core\Language\TranslationInterface objects.
+   */
+  public function __construct() {
+    $this->translators = func_get_args();
+  }
+
+  /**
+   * Implements Drupal\Core\Translation\TranslationInterface::translate()
+   */
+  public function translate($langcode, $string, $context) {
+    foreach ($this->translators as $translator) {
+      $translation = $translator->translate($langcode, $string, $context);
+      if ($translation !== FALSE) {
+        return $translation;
+      }
+    }
+    // No translator got a translation.
+    return FALSE;
+  }
+
+  /**
+   * Implements Drupal\Core\Language\TranslationInterface::reset()
+   */
+  public function reset() {
+    foreach ($this->translators as $translator) {
+      $translator->reset();
+    }
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Translation/TranslationInterface.php b/core/lib/Drupal/Core/Translation/TranslationInterface.php
new file mode 100644
index 0000000..ff76ead
--- /dev/null
+++ b/core/lib/Drupal/Core/Translation/TranslationInterface.php
@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Language\TranslationInterface.
+ */
+
+namespace Drupal\Core\Translation;
+
+/**
+ * Interface for objects capable of string translation.
+ */
+interface TranslationInterface {
+
+  /**
+   * Translates English string to given language.
+   *
+   * @param $langcode
+   *   Language code to translate to.
+   * @param string $string
+   *   The source string
+   * @param array $context
+   *   The string context
+   *
+   * @return string|FALSE
+   *   Translated string if there is a translation, FALSE if not.
+   */
+  public function translate($langcode, $string, $context);
+
+  /**
+   * Resets translation cache.
+   *
+   * Since most translation systems implement some form of caching, this
+   * provides a way to delete that cache.
+   */
+  public function reset();
+
+}
diff --git a/core/modules/locale/lib/Drupal/locale/Gettext.php b/core/modules/locale/lib/Drupal/locale/Gettext.php
index a7c37ca..a078e77 100644
--- a/core/modules/locale/lib/Drupal/locale/Gettext.php
+++ b/core/modules/locale/lib/Drupal/locale/Gettext.php
@@ -21,33 +21,6 @@
  * - File public://*.po to database
  */
 class Gettext {
-
-  /**
-   * Reads the given Gettext PO files into a data structure.
-   *
-   * @param string $langcode
-   *   Language code string.
-   * @param array $files
-   *   List of file objects with URI properties pointing to read.
-   *
-   * @return array
-   *   Structured array as produced by a PoMemoryWriter.
-   *
-   * @see Drupal\Component\Gettext\PoMemoryWriter
-   */
-  static function filesToArray($langcode, array $files) {
-    $writer = new PoMemoryWriter();
-    $writer->setLangcode($langcode);
-    foreach ($files as $file) {
-      $reader = new PoStreamReader();
-      $reader->setURI($file->uri);
-      $reader->setLangcode($langcode);
-      $reader->open();
-      $writer->writeItems($reader, -1);
-    }
-    return $writer->getData();
-  }
-
   /**
    * Reads the given PO files into the database.
    *
diff --git a/core/modules/locale/lib/Drupal/locale/LocaleBundle.php b/core/modules/locale/lib/Drupal/locale/LocaleBundle.php
new file mode 100644
index 0000000..6fad4f1
--- /dev/null
+++ b/core/modules/locale/lib/Drupal/locale/LocaleBundle.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\locale\LocaleBundle.
+ */
+
+namespace Drupal\locale;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Reference;
+use Symfony\Component\HttpKernel\Bundle\Bundle;
+
+use Drupal\Core\Database\Database;
+
+/**
+ * Bundle class for locale services.
+ *
+ * Ths is where we register locale services that should run when the module is
+ * enabled. For now only the locale storage that will be used for translations.
+ */
+class LocaleBundle extends Bundle
+{
+  public function build(ContainerBuilder $container) {
+    // Register storage and lookup translation service.
+    $container->register('locale.storage', 'Drupal\locale\StringDatabaseStorage')
+      ->addArgument(new Reference('database'))
+      ->addArgument(array('target' => 'default'));
+    $container->register('locale.translation.lookup', 'Drupal\locale\LocaleTranslation')
+      ->addArgument(new Reference('locale.storage'));
+    // Replace the default translation service, using lookup as the fallback.
+    $container->register('locale.translation', 'Drupal\Core\Translation\TranslationFallback')
+      ->addArgument(new Reference('locale.translation.custom'))
+      ->addArgument(new Reference('locale.translation.lookup'));
+  }
+}
diff --git a/core/modules/locale/lib/Drupal/locale/LocaleLookup.php b/core/modules/locale/lib/Drupal/locale/LocaleLookup.php
index 9dd04f6..2838524 100644
--- a/core/modules/locale/lib/Drupal/locale/LocaleLookup.php
+++ b/core/modules/locale/lib/Drupal/locale/LocaleLookup.php
@@ -29,7 +29,7 @@ class LocaleLookup extends CacheArray {
   protected $context;
 
   /**
-   * The locale storage
+   * The locale storage.
    *
    * @var Drupal\locale\StringStorageInterface
    */
@@ -74,13 +74,7 @@ protected function resolveCacheMiss($offset) {
       $value = TRUE;
     }
     $this->storage[$offset] = $value;
-    // Disabling the usage of string caching allows a module to watch for
-    // the exact list of strings used on a page. From a performance
-    // perspective that is a really bad idea, so we have no user
-    // interface for this. Be careful when turning this option off!
-    if (variable_get('locale_cache_strings', 1)) {
-      $this->persist($offset);
-    }
+    $this->persist($offset);
     return $value;
   }
 }
diff --git a/core/modules/locale/lib/Drupal/locale/LocaleTranslation.php b/core/modules/locale/lib/Drupal/locale/LocaleTranslation.php
new file mode 100644
index 0000000..62c772c
--- /dev/null
+++ b/core/modules/locale/lib/Drupal/locale/LocaleTranslation.php
@@ -0,0 +1,73 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Language\LocaleTranslation.
+ */
+
+namespace Drupal\locale;
+
+use Drupal\Core\Translation\TranslationInterface;
+use Drupal\locale\StringStorageInterface;
+use Drupal\locale\LocaleLookup;
+
+
+/**
+ * String translator using the locale module.
+ *
+ * Full featured translation system using locale's string storage and
+ * database caching.
+ */
+class LocaleTranslation implements TranslationInterface {
+
+  /**
+   * Storage for strings.
+   *
+   * @var Drupal\locale\StringStorageInterface
+   */
+  protected $storage;
+
+  /**
+   * Cached translations
+   *
+   * @var array
+   *   Array of Drupal\locale\LocaleLookup objects indexed by language code
+   *   and context.
+   */
+  protected $translations;
+
+  /**
+   * Constructs a translator using a string storage.
+   *
+   * @param Drupal\locale\StringStorageInterface $storage
+   *   Storage to use when looking for new translations.
+   */
+  public function __construct($storage) {
+    $this->storage = $storage;
+  }
+
+  /**
+   * Implements Drupal\Core\Translation\TranslationInterface::translate()
+   */
+  public function translate($langcode, $string, $context) {
+    // If the language is not suitable for locale module, just return.
+    if ($langcode == LANGUAGE_SYSTEM || ($langcode == 'en' && !variable_get('locale_translate_english', FALSE))) {
+      return FALSE;
+    }
+    // Strings are cached by langcode, context and roles, using instances of the
+    // LocaleLookup class to handle string lookup and caching.
+    if (!isset($this->translations[$langcode][$context])) {
+      $this->translations[$langcode][$context] = new LocaleLookup($langcode, $context, $this->storage);
+    }
+    $translation = $this->translations[$langcode][$context][$string];
+    return $translation === TRUE ? FALSE : $translation;
+  }
+
+  /**
+   * Implements Drupal\Core\Language\TranslationInterface::reset()
+   */
+  public function reset() {
+    $this->translations = array();
+  }
+
+}
diff --git a/core/modules/locale/lib/Drupal/locale/StringDatabaseStorage.php b/core/modules/locale/lib/Drupal/locale/StringDatabaseStorage.php
index 33138e7..0b0d664 100644
--- a/core/modules/locale/lib/Drupal/locale/StringDatabaseStorage.php
+++ b/core/modules/locale/lib/Drupal/locale/StringDatabaseStorage.php
@@ -284,40 +284,19 @@ protected function dbStringTable($string) {
    *
    * @param Drupal\locale\StringInterface $string
    *   The string object.
-   * @param string $table
-   *   (optional) The table name.
    *
    * @return array
    *   Array with key fields if the string has all keys, or empty array if not.
    */
-  protected function dbStringKeys($string, $table = NULL) {
-    $table = $table ? $table : $this->dbStringTable($string);
-    if ($table && $schema = drupal_get_schema($table)) {
-      $keys = $schema['primary key'];
-      $values = $string->getValues($keys);
-      if (count($values) == count($keys)) {
-        return $values;
-      }
+  protected function dbStringKeys($string) {
+    if ($string->isSource()) {
+      $keys = array('lid');
     }
-    return NULL;
-  }
-
-  /**
-   * Gets field values from a string object that are in the database table.
-   *
-   * @param Drupal\locale\StringInterface $string
-   *   The string object.
-   * @param string $table
-   *   (optional) The table name.
-   *
-   * @return array
-   *   Array with field values indexed by field name.
-   */
-  protected function dbStringValues($string, $table = NULL) {
-    $table = $table ? $table : $this->dbStringTable($string);
-    if ($table && $schema = drupal_get_schema($table)) {
-      $fields = array_keys($schema['fields']);
-      return $string->getValues($fields);
+    elseif ($string->isTranslation()) {
+      $keys = array('lid', 'language');
+    }
+    if (!empty($keys) && ($values = $string->getValues($keys)) && count($keys) == count($values)) {
+      return $values;
     }
     else {
       return array();
@@ -325,27 +304,6 @@ protected function dbStringValues($string, $table = NULL) {
   }
 
   /**
-   * Sets default values from storage.
-   *
-   * @param Drupal\locale\StringInterface $string
-   *   The string object.
-   * @param string $table
-   *   (optional) The table name.
-   */
-  protected function dbStringDefaults($string, $table = NULL) {
-    $table = $table ? $table : $this->dbStringTable($string);
-    if ($table && $schema = drupal_get_schema($table)) {
-      $values = array();
-      foreach ($schema['fields'] as $name => $info) {
-        if (isset($info['default'])) {
-          $values[$name] = $info['default'];
-        }
-      }
-      $string->setValues($values, FALSE);
-    }
-  }
-
-  /**
    * Loads multiple string objects.
    *
    * @param array $conditions
@@ -500,9 +458,16 @@ protected function dbStringSelect(array $conditions, array $options = array()) {
    *   If the string is not suitable for this storage, an exception ithrown.
    */
   protected function dbStringInsert($string) {
-    if (($table = $this->dbStringTable($string)) && ($fields = $this->dbStringValues($string, $table))) {
-      $this->dbStringDefaults($string, $table);
-      return $this->connection->insert($table, $this->options)
+    if ($string->isSource()) {
+      $string->setValues(array('context' => '', 'version' => 'none'), FALSE);
+      $fields = $string->getValues(array('source', 'context', 'version'));
+    }
+    elseif ($string->isTranslation()) {
+      $string->setValues(array('customized' => 0), FALSE);
+      $fields = $string->getValues(array('lid', 'language', 'translation', 'customized'));
+    }
+    if (!empty($fields)) {
+      return $this->connection->insert($this->dbStringTable($string), $this->options)
         ->fields($fields)
         ->execute();
     }
@@ -527,13 +492,17 @@ protected function dbStringInsert($string) {
    *   If the string is not suitable for this storage, an exception is thrown.
    */
   protected function dbStringUpdate($string) {
-    if (($table = $this->dbStringTable($string)) && ($keys = $this->dbStringKeys($string, $table)) &&
-        ($fields = $this->dbStringValues($string, $table)) && ($values = array_diff_key($fields, $keys)))
-    {
-      return $this->connection->merge($table, $this->options)
-      ->key($keys)
-      ->fields($values)
-      ->execute();
+    if ($string->isSource()) {
+      $values = $string->getValues(array('source', 'context', 'version'));
+    }
+    elseif ($string->isTranslation()) {
+      $values = $string->getValues(array('translation', 'customized'));
+    }
+    if (!empty($values) && $keys = $this->dbStringKeys($string)) {
+      return $this->connection->merge($this->dbStringTable($string), $this->options)
+        ->key($keys)
+        ->fields($values)
+        ->execute();
     }
     else {
       throw new StringStorageException(format_string('The string cannot be updated: @string', array(
diff --git a/core/modules/locale/lib/Drupal/locale/Tests/LocaleExportTest.php b/core/modules/locale/lib/Drupal/locale/Tests/LocaleExportTest.php
index 7ae1bf7..816b726 100644
--- a/core/modules/locale/lib/Drupal/locale/Tests/LocaleExportTest.php
+++ b/core/modules/locale/lib/Drupal/locale/Tests/LocaleExportTest.php
@@ -79,9 +79,11 @@ function testExportTranslation() {
     ), t('Import'));
     drupal_unlink($name);
 
-    // We can't import a string with an empty translation, but calling
-    // locale() for an new string creates an entry in the locales_source table.
-    locale('February', NULL, 'fr');
+    // Create string without translation in the locales_source table.
+    locale_storage()
+      ->createString()
+      ->setString('February')
+      ->save();
 
     // Export only customized French translations.
     $this->drupalPost('admin/config/regional/translate/export', array(
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index 3ebe97d..8f3a711 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -16,6 +16,7 @@
 use Drupal\locale\StringDatabaseStorage;
 use Drupal\locale\TranslationsStream;
 use Drupal\Core\Database\Database;
+use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 
 /**
  * Regular expression pattern used to localize JavaScript strings.
@@ -291,76 +292,21 @@ function locale_translatable_language_list() {
 }
 
 /**
- * Provides interface translation services.
- *
- * This function is called from t() to translate a string if needed.
- *
- * @param $string
- *   A string to look up translation for. If omitted, all the
- *   cached strings will be returned in all languages already
- *   used on the page.
- * @param $context
- *   The context of this string.
- * @param $langcode
- *   Language code to use for the lookup.
- */
-function locale($string = NULL, $context = NULL, $langcode = NULL) {
-  $language_interface = language(LANGUAGE_TYPE_INTERFACE);
-
-  // Use the advanced drupal_static() pattern, since this is called very often.
-  static $drupal_static_fast;
-  if (!isset($drupal_static_fast)) {
-    $drupal_static_fast['locale'] = &drupal_static(__FUNCTION__, array('cache' => array(), 'exists' => NULL));
-  }
-  $locale_t = &$drupal_static_fast['locale']['cache'];
-  $locale_exists = &$drupal_static_fast['locale']['exists'];
-
-  // Check whether Locale module is actually installed and operational.
-  // The mere existence of locale() does not imply that Locale module is
-  // actually enabled and its database tables are installed. Since PHP code
-  // cannot be unloaded, this is typically the case in the environment that
-  // is executing a test.
-  if (!isset($locale_exists)) {
-    $locale_exists = function_exists('module_exists') && module_exists('locale');
-  }
-  if (!$locale_exists) {
-    return $string;
-  }
-
-  if (!isset($string)) {
-    // Return all cached strings if no string was specified
-    return $locale_t;
-  }
-
-  $langcode = isset($langcode) ? $langcode : $language_interface->langcode;
-
-  // Strings are cached by langcode, context and roles, using instances of the
-  // LocaleLookup class to handle string lookup and caching.
-  if (!isset($locale_t[$langcode][$context]) && isset($language_interface)) {
-    $locale_t[$langcode][$context] = new LocaleLookup($langcode, $context, locale_storage());
-  }
-  return ($locale_t[$langcode][$context][$string] === TRUE ? $string : $locale_t[$langcode][$context][$string]);
-}
-
-/**
- * Reset static variables used by locale().
- */
-function locale_reset() {
-  drupal_static_reset('locale');
-}
-
-/**
- * Gets the locale storage controller class .
+ * Gets the locale storage controller.
  *
  * @return Drupal\locale\StringStorageInterface
  */
 function locale_storage() {
-  $storage = &drupal_static(__FUNCTION__);
-  if (!isset($storage)) {
-    $options = array('target' => 'default');
-    $storage = new StringDatabaseStorage(Database::getConnection($options['target']), $options);
+  try {
+    return drupal_container()->get('locale.storage');
+  }
+  catch (InvalidArgumentException $e) {
+    // The locale storage is not initialized yet, which happens when
+    // regenerating JavaScript strings during updates.
+    $storage = new StringDatabaseStorage(drupal_container()->get('database'), array('target' => 'default'));
+    drupal_container()->set('locale.storage', $storage);
+    return $storage;
   }
-  return $storage;
 }
 
 /**
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/InstallerLanguageTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/InstallerLanguageTest.php
index 9960d4c..19d78cf 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/InstallerLanguageTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/InstallerLanguageTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\system\Tests\Common;
 
 use Drupal\simpletest\WebTestBase;
+use Drupal\Core\Translation\FileTranslation;
 
 /**
  * Tests installer language detection.
@@ -41,9 +42,9 @@ function testInstallerTranslationFiles() {
       'hu' => array('drupal-8.0.hu.po'),
       'it' => array(),
     );
-
+    $file_translation = new FileTranslation(variable_get('locale_translate_file_directory'));
     foreach ($expected_translation_files as $langcode => $files_expected) {
-      $files_found = install_find_translation_files($langcode);
+      $files_found = $file_translation->findTranslationFiles($langcode);
       $this->assertTrue(count($files_found) == count($files_expected), format_string('@count installer languages found.', array('@count' => count($files_expected))));
       foreach ($files_found as $file) {
         $this->assertTrue(in_array($file->filename, $files_expected), format_string('@file found.', array('@file' => $file->filename)));