reverted:
--- b/core/modules/language/language.install
+++ /dev/null
@@ -1,26 +0,0 @@
-<?php
-
-/**
- * @file
- * Install, update and uninstall functions for the language module.
- */
-
-/**
- * Implements hook_install().
- */
-function language_install() {
-  // Get all the existing modules that are enabled and install any language
-  // configuration.
-  $language_config_override = \Drupal::service('language.config_factory_override');
-  foreach (array_keys(\Drupal::moduleHandler()->getModuleList()) as $module) {
-    $language_config_override->install('module', $module);
-  }
-  /** @var \Drupal\Core\Extension\ThemeHandler $theme_handler */
-  $theme_handler = \Drupal::service('theme_handler');
-  foreach ($theme_handler->listInfo() as $theme) {
-    if ($theme->status) {
-      $language_config_override->install('theme', $theme->name);
-    }
-  }
-  \Drupal::configFactory()->reset();
-}
diff -u b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
--- b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
+++ b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\language\Config;
 
+use Drupal\Core\Config\ExtensionInstallStorage;
 use Drupal\Core\Config\FileStorage;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Config\TypedConfigManagerInterface;
@@ -102,7 +103,7 @@
    */
   public function getStorage($langcode) {
     if (!isset($this->storages[$langcode])) {
-      $this->storages[$langcode] = $this->baseStorage->createCollection('language.' . $langcode);
+      $this->storages[$langcode] = $this->baseStorage->createCollection($this->createConfigCollectionName($langcode));
     }
     return $this->storages[$langcode];
   }
@@ -142,21 +143,13 @@
    */
   public function install($type, $name) {
     // Work out if this extension provides default language overrides.
-    $config_dir = drupal_get_path($type, $name) . '/config/install/language';
-    if (is_dir($config_dir)) {
-      // List all the directories.
-      // \DirectoryIterator on Windows requires an absolute path.
-      $it  = new \DirectoryIterator(realpath($config_dir));
-      foreach ($it as $dir) {
-        if (!$dir->isDot() && $dir->isDir() ) {
-          $default_language_config = new FileStorage($dir->getPathname());
-          $storage = $this->getStorage($dir->getFilename());
-          foreach ($default_language_config->listAll() as $config_name) {
-            $data = $default_language_config->read($config_name);
-            $config = new LanguageConfigOverride($config_name, $storage, $this->typedConfigManager);
-            $config->setData($data)->save();
-          }
-        }
+    foreach (\Drupal::languageManager()->getLanguages() as $language) {
+      $install_storage = new ExtensionInstallStorage($this->baseStorage, ExtensionInstallStorage::CONFIG_INSTALL_DIRECTORY, $this->createConfigCollectionName($language->getId()));
+      $storage = $this->getStorage($language->getId());
+      foreach ($install_storage->listAll() as $config_name) {
+        $data = $install_storage->read($config_name);
+        $config = new LanguageConfigOverride($config_name, $storage, $this->typedConfigManager);
+        $config->setData($data)->save();
       }
     }
   }
@@ -173,2 +166,15 @@
 
+  /**
+   * Creates a configuration collection name based on a langcode.
+   *
+   * @param $langcode
+   *   The langcode.
+   *
+   * @return string
+   *   The configuration collection name for a langcode.
+   */
+  protected function createConfigCollectionName($langcode) {
+    return 'language.' . $langcode;
+  }
+
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Config/ExtensionInstallStorage.php
+++ b/core/lib/Drupal/Core/Config/ExtensionInstallStorage.php
@@ -32,9 +32,10 @@ class ExtensionInstallStorage extends InstallStorage {
    *   The directory to scan in each extension to scan for files. Defaults to
    *   'config'.
    */
-  public function __construct(StorageInterface $config_storage, $directory = self::CONFIG_INSTALL_DIRECTORY) {
+  public function __construct(StorageInterface $config_storage, $directory = self::CONFIG_INSTALL_DIRECTORY, $collection = self::DEFAULT_COLLECTION) {
     $this->configStorage = $config_storage;
     $this->directory = $directory;
+    $this->collection = $collection;
   }
 
   /**
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Config/InstallStorage.php
+++ b/core/lib/Drupal/Core/Config/InstallStorage.php
@@ -53,8 +53,9 @@ class InstallStorage extends FileStorage {
    *   The directory to scan in each extension to scan for files. Defaults to
    *   'config'.
    */
-  public function __construct($directory = self::CONFIG_INSTALL_DIRECTORY) {
+  public function __construct($directory = self::CONFIG_INSTALL_DIRECTORY, $collection = self::DEFAULT_COLLECTION) {
     $this->directory = $directory;
+    $this->collection = $collection;
   }
 
   /**
@@ -198,7 +199,7 @@ public function getComponentNames($type, array $list) {
    *   The configuration folder name for this component.
    */
   protected function getComponentFolder($type, $name) {
-    return drupal_get_path($type, $name) . '/' . $this->directory;
+    return drupal_get_path($type, $name) . '/' . $this->getCollectionDirectory();
   }
 
   /**
only in patch2:
unchanged:
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigLanguageOverrideTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigLanguageOverrideTest.php
@@ -32,6 +32,14 @@ public static function getInfo() {
 
   public function setUp() {
     parent::setUp();
+    language_save(new Language(array(
+      'name' => 'French',
+      'id' => 'fr',
+    )));
+    language_save(new Language(array(
+      'name' => 'German',
+      'id' => 'de',
+    )));
     $this->installConfig(array('config_test'));
   }
 
@@ -50,15 +58,6 @@ function testConfigLanguageOverride() {
     $raw = $config->getRawData();
     $this->assertIdentical($raw['foo'], 'bar');
 
-    language_save(new Language(array(
-      'name' => 'French',
-      'id' => 'fr',
-    )));
-    language_save(new Language(array(
-      'name' => 'German',
-      'id' => 'de',
-    )));
-
     \Drupal::languageManager()->setConfigOverrideLanguage(language_load('fr'));
     $config = \Drupal::config('config_test.system');
     $this->assertIdentical($config->get('foo'), 'fr bar');