diff --git a/core/lib/Drupal.php b/core/lib/Drupal.php
index 141686f..a891254 100644
--- a/core/lib/Drupal.php
+++ b/core/lib/Drupal.php
@@ -628,4 +628,20 @@ public static function accessManager() {
     return static::$container->get('access_manager');
   }
 
+  /**
+   * Returns a class instance with a given class definition.
+   *
+   * @param string $definition
+   *   A class name or service name.
+   *
+   * @throws \InvalidArgumentException
+   *   If $class is not a valid service identifier and the class does not exist.
+   *
+   * @return object
+   *   The instance of the class.
+   */
+  public static function resolve($definition) {
+    return static::$container->get('class_resolver')->getInstanceFromDefinition($definition);
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Form/FormAlterInterface.php b/core/lib/Drupal/Core/Form/FormAlterInterface.php
new file mode 100644
index 0000000..9a3565e
--- /dev/null
+++ b/core/lib/Drupal/Core/Form/FormAlterInterface.php
@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Form\FormAlterInterface.
+ */
+
+namespace Drupal\Core\Form;
+
+/**
+ * An interface for performing form alters using an object.
+ *
+ * @code
+ * function mymodule_FORMID_alter(&$form, FormStateInterface $form_state) {
+ *   $alter = \Drupal::resolve('CLASSNAME');
+ *   $alter->alter($form, $form_state);
+ * }
+ * @endcode
+ */
+interface FormAlterInterface {
+
+  /**
+   * Alters the form array.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function alter(array &$form, FormStateInterface $form_state);
+}
diff --git a/core/lib/Drupal/Core/Form/FormAlterSubmitInterface.php b/core/lib/Drupal/Core/Form/FormAlterSubmitInterface.php
new file mode 100644
index 0000000..6438ab9
--- /dev/null
+++ b/core/lib/Drupal/Core/Form/FormAlterSubmitInterface.php
@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Form\FormAlterSubmitInterface.
+ */
+
+namespace Drupal\Core\Form;
+
+/**
+ * An interface for performing form alters that add a submit handler.
+ *
+ * The FormAlterInterface::alter() method is responsible for adding the submit
+ * handler to the form.
+ */
+interface FormAlterSubmitInterface extends FormAlterInterface {
+
+  /**
+   * Submit handler for the form alter.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function submit(array &$form, FormStateInterface $form_state);
+}
diff --git a/core/lib/Drupal/Core/Form/FormAlterValidateInterface.php b/core/lib/Drupal/Core/Form/FormAlterValidateInterface.php
new file mode 100644
index 0000000..c07df3d
--- /dev/null
+++ b/core/lib/Drupal/Core/Form/FormAlterValidateInterface.php
@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Form\FormAlterInterface.
+ */
+
+namespace Drupal\Core\Form;
+
+/**
+ * An interface for performing form alters that add a validation handler.
+ *
+ * The FormAlterInterface::alter() method is responsible for adding the
+ * validation handler to the form.
+ */
+interface FormAlterValidateInterface extends FormAlterInterface {
+
+  /**
+   * Validation handler for the form alter.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function validate(array &$form, FormStateInterface $form_state);
+}
diff --git a/core/modules/contact/contact.module b/core/modules/contact/contact.module
index 0ad6093..54623e2 100644
--- a/core/modules/contact/contact.module
+++ b/core/modules/contact/contact.module
@@ -147,33 +147,9 @@ function contact_mail($key, &$message, $params) {
  * @see \Drupal\user\ProfileForm::form()
  */
 function contact_form_user_form_alter(&$form, FormStateInterface $form_state) {
-  $form['contact'] = array(
-    '#type' => 'details',
-    '#title' => t('Contact settings'),
-    '#open' => TRUE,
-    '#weight' => 5,
-  );
-  $account = $form_state->getFormObject()->getEntity();
-  if (!\Drupal::currentUser()->isAnonymous() && $account->id()) {
-    $account_data = \Drupal::service('user.data')->get('contact', $account->id(), 'enabled');
-  }
-  $form['contact']['contact'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Personal contact form'),
-    '#default_value' => isset($account_data) ? $account_data : \Drupal::config('contact.settings')->get('user_default_enabled'),
-    '#description' => t('Allow other users to contact you via a personal contact form which keeps your email address hidden. Note that some privileged users such as site administrators are still able to contact you even if you choose to disable this feature.'),
-  );
-  $form['actions']['submit']['#submit'][] = 'contact_user_profile_form_submit';
-}
-
-/**
- * Submit callback for the user profile form to save the contact page setting.
- */
-function contact_user_profile_form_submit($form, FormStateInterface $form_state) {
-  $account = $form_state->getFormObject()->getEntity();
-  if ($account->id() && $form_state->hasValue('contact')) {
-    \Drupal::service('user.data')->set('contact', $account->id(), 'enabled', (int) $form_state->getValue('contact'));
-  }
+  /** @var \Drupal\contact\Form\UserFormAlter $alter */
+  $alter = \Drupal::resolve('Drupal\contact\Form\UserFormAlter');
+  $alter->alter($form, $form_state);
 }
 
 /**
@@ -181,32 +157,10 @@ function contact_user_profile_form_submit($form, FormStateInterface $form_state)
  *
  * Add the default personal contact setting on the user settings page.
  *
- * @see user_admin_settings()
+ * @see \Drupal\user\AccountSettingsForm
  */
 function contact_form_user_admin_settings_alter(&$form, FormStateInterface $form_state) {
-  $form['contact'] = array(
-    '#type' => 'details',
-    '#title' => t('Contact settings'),
-    '#open' => TRUE,
-    '#weight' => 0,
-  );
-  $form['contact']['contact_default_status'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Enable the personal contact form by default for new users'),
-    '#description' => t('Changing this setting will not affect existing users.'),
-    '#default_value' => \Drupal::config('contact.settings')->get('user_default_enabled'),
-  );
-  // Add submit handler to save contact configuration.
-  $form['#submit'][] = 'contact_form_user_admin_settings_submit';
-}
-
-/**
- * Form submission handler for user_admin_settings().
- *
- * @see contact_form_user_admin_settings_alter()
- */
-function contact_form_user_admin_settings_submit($form, FormStateInterface $form_state) {
-  \Drupal::config('contact.settings')
-    ->set('user_default_enabled', $form_state->getValue('contact_default_status'))
-    ->save();
+  /** @var \Drupal\contact\Form\UserAccountSettingsFormAlter $alter */
+  $alter = \Drupal::resolve('Drupal\contact\Form\UserAccountSettingsFormAlter');
+  $alter->alter($form, $form_state);
 }
diff --git a/core/modules/contact/src/Form/UserAccountSettingsFormAlter.php b/core/modules/contact/src/Form/UserAccountSettingsFormAlter.php
new file mode 100644
index 0000000..4cbcb07
--- /dev/null
+++ b/core/modules/contact/src/Form/UserAccountSettingsFormAlter.php
@@ -0,0 +1,74 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\contact\Form\UserAccountSettingsFormAlter.
+ */
+
+namespace Drupal\contact\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
+use Drupal\Core\Form\FormAlterSubmitInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Adds the default personal contact setting on the user settings page.
+ *
+ * @see \Drupal\user\AccountSettingsForm
+ */
+class UserAccountSettingsFormAlter implements FormAlterSubmitInterface, ContainerInjectionInterface {
+  use DependencySerializationTrait;
+  use StringTranslationTrait;
+
+  /**
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory) {
+    $this->configFactory = $config_factory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('config.factory')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alter(array &$form, FormStateInterface $form_state) {
+    $form['contact'] = array(
+      '#type' => 'details',
+      '#title' => $this->t('Contact settings'),
+      '#open' => TRUE,
+      '#weight' => 0,
+    );
+    $form['contact']['contact_default_status'] = array(
+      '#type' => 'checkbox',
+      '#title' => $this->t('Enable the personal contact form by default for new users'),
+      '#description' => $this->t('Changing this setting will not affect existing users.'),
+      // @see \Drupal\Core\Form\ConfigFormBase::config()
+      '#default_value' => $this->configFactory->get('contact.settings')->getOriginal('user_default_enabled', FALSE),
+    );
+    // Add submit handler to save contact configuration.
+    $form['#submit'][] = array($this, 'submit');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submit(array &$form, FormStateInterface $form_state) {
+    $this->configFactory->get('contact.settings')
+      ->set('user_default_enabled', $form_state->getValue('contact_default_status'))
+      ->save();
+  }
+
+}
diff --git a/core/modules/contact/src/Form/UserFormAlter.php b/core/modules/contact/src/Form/UserFormAlter.php
new file mode 100644
index 0000000..d43c895
--- /dev/null
+++ b/core/modules/contact/src/Form/UserFormAlter.php
@@ -0,0 +1,87 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\contact\Form\UserFormAlter.
+ */
+
+namespace Drupal\contact\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
+use Drupal\Core\Form\FormAlterSubmitInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Session\AccountProxyInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\user\UserDataInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Adds the enable personal contact checkbox to a user's account page.
+ *
+ * @see \Drupal\user\ProfileForm
+ */
+class UserFormAlter implements FormAlterSubmitInterface, ContainerInjectionInterface {
+  use DependencySerializationTrait;
+  use StringTranslationTrait;
+
+  /**
+   * @param \Drupal\Core\Session\AccountProxyInterface $current_user
+   *   The current user.
+   * @param \Drupal\user\UserDataInterface $user_data
+   *   The user data service.
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   */
+  public function __construct(AccountProxyInterface $current_user, UserDataInterface $user_data, ConfigFactoryInterface $config_factory) {
+    $this->currentUser = $current_user;
+    $this->userData = $user_data;
+    $this->configFactory = $config_factory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('current_user'),
+      $container->get('user.data'),
+      $container->get('config.factory')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alter(array &$form, FormStateInterface $form_state) {
+    $form['contact'] = array(
+      '#type' => 'details',
+      '#title' => $this->t('Contact settings'),
+      '#open' => TRUE,
+      '#weight' => 5,
+    );
+    $account = $form_state->getFormObject()->getEntity();
+    if (!$this->currentUser->isAnonymous() && $account->id()) {
+      $account_data = $this->userData->get('contact', $account->id(), 'enabled');
+    }
+    $form['contact']['contact'] = array(
+      '#type' => 'checkbox',
+      '#title' => $this->t('Personal contact form'),
+      '#default_value' => isset($account_data) ? $account_data : $this->configFactory->get('contact.settings')->get('user_default_enabled'),
+      '#description' => $this->t('Allow other users to contact you via a personal contact form which keeps your email address hidden. Note that some privileged users such as site administrators are still able to contact you even if you choose to disable this feature.'),
+    );
+    $form['actions']['submit']['#submit'][] = array($this, 'submit');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submit(array &$form, FormStateInterface $form_state) {
+    $account = $form_state->getFormObject()->getEntity();
+    if ($account->id() && $form_state->hasValue('contact')) {
+      $this->userData->set('contact', $account->id(), 'enabled', (int) $form_state->getValue('contact'));
+    }
+  }
+
+}
diff --git a/core/modules/dblog/dblog.module b/core/modules/dblog/dblog.module
index e8568d4..07d4fe9 100644
--- a/core/modules/dblog/dblog.module
+++ b/core/modules/dblog/dblog.module
@@ -94,23 +94,7 @@ function _dblog_get_message_types() {
  * Implements hook_form_FORM_ID_alter() for system_logging_settings().
  */
 function dblog_form_system_logging_settings_alter(&$form, FormStateInterface $form_state) {
-  $row_limits = array(100, 1000, 10000, 100000, 1000000);
-  $form['dblog_row_limit'] = array(
-    '#type' => 'select',
-    '#title' => t('Database log messages to keep'),
-    '#default_value' => \Drupal::config('dblog.settings')->get('row_limit'),
-    '#options' => array(0 => t('All')) + array_combine($row_limits, $row_limits),
-    '#description' => t('The maximum number of messages to keep in the database log. Requires a <a href="@cron">cron maintenance task</a>.', array('@cron' => \Drupal::url('system.status')))
-  );
-
-  $form['#submit'][] = 'dblog_logging_settings_submit';
-}
-
-/**
- * Form submission handler for system_logging_settings().
- *
- * @see dblog_form_system_logging_settings_alter()
- */
-function dblog_logging_settings_submit($form, FormStateInterface $form_state) {
-  \Drupal::config('dblog.settings')->set('row_limit', $form_state->getValue('dblog_row_limit'))->save();
+  /** @var \Drupal\dblog\Form\SystemLoggingSettingsFormAlter $alter */
+  $alter = \Drupal::resolve('Drupal\dblog\Form\SystemLoggingSettingsFormAlter');
+  $alter->alter($form, $form_state);
 }
diff --git a/core/modules/dblog/src/Form/SystemLoggingSettingsFormAlter.php b/core/modules/dblog/src/Form/SystemLoggingSettingsFormAlter.php
new file mode 100644
index 0000000..520e314
--- /dev/null
+++ b/core/modules/dblog/src/Form/SystemLoggingSettingsFormAlter.php
@@ -0,0 +1,73 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\dblog\Form\SystemLoggingSettingsFormAlter.
+ */
+
+namespace Drupal\dblog\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
+use Drupal\Core\Form\FormAlterSubmitInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Routing\UrlGeneratorTrait;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Alters the logging form to add dblog settings.
+ *
+ * @see \Drupal\system\Form\LoggingForm
+ */
+class SystemLoggingSettingsFormAlter implements FormAlterSubmitInterface, ContainerInjectionInterface {
+  use DependencySerializationTrait;
+  use StringTranslationTrait;
+  use UrlGeneratorTrait;
+
+  /**
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory) {
+    $this->configFactory = $config_factory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('config.factory')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alter(array &$form, FormStateInterface $form_state) {
+    $row_limits = array(100, 1000, 10000, 100000, 1000000);
+    $form['dblog_row_limit'] = array(
+      '#type' => 'select',
+      '#title' => $this->t('Database log messages to keep'),
+      '#default_value' => $this->configFactory->get('dblog.settings')->getOriginal('row_limit', FALSE),
+      '#options' => array(0 => $this->t('All')) + array_combine($row_limits, $row_limits),
+      '#description' => $this->t('The maximum number of messages to keep in the database log. Requires a <a href="@cron">cron maintenance task</a>.', array('@cron' => $this->url('system.status')))
+    );
+    $form['#submit'][] = array($this, 'submit');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submit(array &$form, FormStateInterface $form_state) {
+    $this->configFactory->get('dblog.settings')->set('row_limit', $form_state->getValue('dblog_row_limit'))->save();
+  }
+
+}
diff --git a/core/modules/language/src/Form/ContentLanguageSettingsForm.php b/core/modules/language/src/Form/ContentLanguageSettingsForm.php
index 1e89850..67b455f 100644
--- a/core/modules/language/src/Form/ContentLanguageSettingsForm.php
+++ b/core/modules/language/src/Form/ContentLanguageSettingsForm.php
@@ -136,7 +136,15 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       }
     }
 
-    $form = parent::buildForm($form, $form_state);
+    $form['actions']['#type'] = 'actions';
+    $form['actions']['submit'] = array(
+      '#type' => 'submit',
+      '#value' => $this->t('Save configuration'),
+      '#button_type' => 'primary',
+    );
+
+    // By default, render the form using theme_system_config_form().
+    $form['#theme'] = 'system_config_form';
 
     return $form;
   }
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index 3a75398..adfb167 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -835,27 +835,12 @@ function node_page_top(array &$page) {
  *
  * Alters the theme form to use the admin theme on node editing.
  *
- * @see node_form_system_themes_admin_form_submit()
+ * @see \Drupal\system\Form\ThemeAdminForm
  */
-function node_form_system_themes_admin_form_alter(&$form, FormStateInterface $form_state, $form_id) {
-  $form['admin_theme']['use_admin_theme'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Use the administration theme when editing or creating content'),
-    '#default_value' => \Drupal::config('node.settings')->get('use_admin_theme'),
-  );
-  $form['#submit'][] = 'node_form_system_themes_admin_form_submit';
-}
-
-/**
- * Form submission handler for system_themes_admin_form().
- *
- * @see node_form_system_themes_admin_form_alter()
- */
-function node_form_system_themes_admin_form_submit($form, FormStateInterface $form_state) {
-  \Drupal::config('node.settings')
-    ->set('use_admin_theme', $form_state->getValue('use_admin_theme'))
-    ->save();
-  \Drupal::service('router.builder_indicator')->setRebuildNeeded();
+function node_form_system_themes_admin_form_alter(&$form, FormStateInterface $form_state) {
+  /** @var \Drupal\node\Form\SystemThemesAdminFormAlter $alter */
+  $alter = \Drupal::resolve('Drupal\node\Form\SystemThemesAdminFormAlter');
+  $alter->alter($form, $form_state);
 }
 
 /**
diff --git a/core/modules/node/src/Form/SystemThemesAdminFormAlter.php b/core/modules/node/src/Form/SystemThemesAdminFormAlter.php
new file mode 100644
index 0000000..030176c
--- /dev/null
+++ b/core/modules/node/src/Form/SystemThemesAdminFormAlter.php
@@ -0,0 +1,87 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\node\Form\SystemThemesAdminFormAlter.
+ */
+
+namespace Drupal\node\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
+use Drupal\Core\Form\FormAlterSubmitInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Routing\RouteBuilderIndicatorInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Alters the theme form to use the admin theme on node editing.
+ *
+ * @see \Drupal\system\Form\ThemeAdminForm
+ */
+class SystemThemesAdminFormAlter implements FormAlterSubmitInterface, ContainerInjectionInterface {
+  use DependencySerializationTrait;
+  use StringTranslationTrait;
+
+  /**
+   * The config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * The route builder indicator service.
+   *
+   * @var \Drupal\Core\Routing\RouteBuilderIndicatorInterface
+   */
+  protected $routeBuilderIndicator;
+
+  /**
+   * Constructs the form alter object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   * @param \Drupal\Core\Routing\RouteBuilderIndicatorInterface $indicator
+   *   The route builder indicator service.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory, RouteBuilderIndicatorInterface $indicator) {
+    $this->configFactory = $config_factory;
+    $this->routeBuilderIndicator = $indicator;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('config.factory'),
+      $container->get('router.builder_indicator')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alter(array &$form, FormStateInterface $form_state) {
+    $form['admin_theme']['use_admin_theme'] = array(
+      '#type' => 'checkbox',
+      '#title' => $this->t('Use the administration theme when editing or creating content'),
+      '#default_value' => $this->configFactory->get('node.settings')->getOriginal('use_admin_theme', FALSE),
+    );
+    $form['#submit'][] = array($this, 'submit');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submit(array &$form, FormStateInterface $form_state) {
+    $this->configFactory->get('node.settings')
+      ->set('use_admin_theme', $form_state->getValue('use_admin_theme'))
+      ->save();
+    $this->routeBuilderIndicator->setRebuildNeeded();
+  }
+
+}
diff --git a/core/modules/syslog/src/Form/SystemLoggingSettingsFormAlter.php b/core/modules/syslog/src/Form/SystemLoggingSettingsFormAlter.php
new file mode 100644
index 0000000..5a8ea5b
--- /dev/null
+++ b/core/modules/syslog/src/Form/SystemLoggingSettingsFormAlter.php
@@ -0,0 +1,132 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\syslog\Form\SystemLoggingSettingsFormAlter.
+ */
+
+namespace Drupal\syslog\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Form\FormAlterSubmitInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Routing\LinkGeneratorTrait;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\Core\Url;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Alters the logging form to add syslog settings.
+ *
+ * @see \Drupal\system\Form\LoggingForm
+ */
+class SystemLoggingSettingsFormAlter implements FormAlterSubmitInterface, ContainerInjectionInterface {
+  use DependencySerializationTrait;
+  use StringTranslationTrait;
+  use LinkGeneratorTrait;
+
+  /**
+   * The config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * Constructs the form alter object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory, ModuleHandlerInterface $module_handler) {
+    $this->configFactory = $config_factory;
+    $this->moduleHandler = $module_handler;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('config.factory'),
+      $container->get('module_handler')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alter(array &$form, FormStateInterface $form_state) {
+    // Prevent configuration overrides from bleeding into stored configuration.
+    $old_state = $this->configFactory->setOverrideState(FALSE);
+    $config = $this->configFactory->get('syslog.settings');
+    $this->configFactory->setOverrideState($old_state);
+
+    $help = $this->moduleHandler->moduleExists('help') ? ' ' . $this->l($this->t('More information'), new Url('help.page', ['name' => 'syslog'])) . '.' : NULL;
+    $form['syslog_identity'] = array(
+      '#type'          => 'textfield',
+      '#title'         => $this->t('Syslog identity'),
+      '#default_value' => $config->get('identity'),
+      '#description'   => $this->t('A string that will be prepended to every message logged to Syslog. If you have multiple sites logging to the same Syslog log file, a unique identity per site makes it easy to tell the log entries apart.') . $help,
+    );
+    if (defined('LOG_LOCAL0')) {
+      $form['syslog_facility'] = array(
+        '#type'          => 'select',
+        '#title'         => $this->t('Syslog facility'),
+        '#default_value' => $config->get('facility'),
+        '#options'       => $this->facilityList(),
+        '#description'   => $this->t('Depending on the system configuration, Syslog and other logging tools use this code to identify or filter messages from within the entire system log.') . $help,
+      );
+    }
+    $form['syslog_format'] = array(
+      '#type'          => 'textarea',
+      '#title'         => $this->t('Syslog format'),
+      '#default_value' => $config->get('format'),
+      '#description'   => $this->t('Specify the format of the syslog entry. Available variables are: <dl><dt><code>!base_url</code></dt><dd>Base URL of the site.</dd><dt><code>!timestamp</code></dt><dd>Unix timestamp of the log entry.</dd><dt><code>!type</code></dt><dd>The category to which this message belongs.</dd><dt><code>!ip</code></dt><dd>IP address of the user triggering the message.</dd><dt><code>!request_uri</code></dt><dd>The requested URI.</dd><dt><code>!referer</code></dt><dd>HTTP Referer if available.</dd><dt><code>!uid</code></dt><dd>User ID.</dd><dt><code>!link</code></dt><dd>A link to associate with the message.</dd><dt><code>!message</code></dt><dd>The message to store in the log.</dd></dl>'),
+    );
+    $form['#submit'][] = array($this, 'submit');
+  }
+
+  /**
+   * Lists all possible syslog facilities for UNIX/Linux.
+   *
+   * @return array
+   *   An array of syslog facilities for UNIX/Linux.
+   */
+  protected function facilityList() {
+    return array(
+      LOG_LOCAL0 => 'LOG_LOCAL0',
+      LOG_LOCAL1 => 'LOG_LOCAL1',
+      LOG_LOCAL2 => 'LOG_LOCAL2',
+      LOG_LOCAL3 => 'LOG_LOCAL3',
+      LOG_LOCAL4 => 'LOG_LOCAL4',
+      LOG_LOCAL5 => 'LOG_LOCAL5',
+      LOG_LOCAL6 => 'LOG_LOCAL6',
+      LOG_LOCAL7 => 'LOG_LOCAL7',
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submit(array &$form, FormStateInterface $form_state) {
+    $this->configFactory->get('syslog.settings')
+      ->set('identity', $form_state->getValue('syslog_identity'))
+      ->set('facility', $form_state->getValue('syslog_facility'))
+      ->set('format', $form_state->getValue('syslog_format'))
+      ->save();
+  }
+
+}
diff --git a/core/modules/syslog/syslog.module b/core/modules/syslog/syslog.module
index aad4060..d89ed06 100644
--- a/core/modules/syslog/syslog.module
+++ b/core/modules/syslog/syslog.module
@@ -5,7 +5,6 @@
  * Redirects logging messages to syslog.
  */
 
-use Drupal\Core\Url;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
 
@@ -33,61 +32,7 @@ function syslog_help($route_name, RouteMatchInterface $route_match) {
  * Implements hook_form_FORM_ID_alter().
  */
 function syslog_form_system_logging_settings_alter(&$form, FormStateInterface $form_state) {
-  $config = \Drupal::config('syslog.settings');
-  $help = \Drupal::moduleHandler()->moduleExists('help') ? ' ' . \Drupal::l(t('More information'), new Url('help.page', ['name' => 'syslog'])) . '.' : NULL;
-  $form['syslog_identity'] = array(
-    '#type'          => 'textfield',
-    '#title'         => t('Syslog identity'),
-    '#default_value' => $config->get('identity'),
-    '#description'   => t('A string that will be prepended to every message logged to Syslog. If you have multiple sites logging to the same Syslog log file, a unique identity per site makes it easy to tell the log entries apart.') . $help,
-  );
-  if (defined('LOG_LOCAL0')) {
-    $form['syslog_facility'] = array(
-      '#type'          => 'select',
-      '#title'         => t('Syslog facility'),
-      '#default_value' => $config->get('facility'),
-      '#options'       => syslog_facility_list(),
-      '#description'   => t('Depending on the system configuration, Syslog and other logging tools use this code to identify or filter messages from within the entire system log.') . $help,
-     );
-  }
-  $form['syslog_format'] = array(
-    '#type'          => 'textarea',
-    '#title'         => t('Syslog format'),
-    '#default_value' => $config->get('format'),
-    '#description'   => t('Specify the format of the syslog entry. Available variables are: <dl><dt><code>!base_url</code></dt><dd>Base URL of the site.</dd><dt><code>!timestamp</code></dt><dd>Unix timestamp of the log entry.</dd><dt><code>!type</code></dt><dd>The category to which this message belongs.</dd><dt><code>!ip</code></dt><dd>IP address of the user triggering the message.</dd><dt><code>!request_uri</code></dt><dd>The requested URI.</dd><dt><code>!referer</code></dt><dd>HTTP Referer if available.</dd><dt><code>!uid</code></dt><dd>User ID.</dd><dt><code>!link</code></dt><dd>A link to associate with the message.</dd><dt><code>!message</code></dt><dd>The message to store in the log.</dd></dl>'),
-  );
-
-  $form['#submit'][] = 'syslog_logging_settings_submit';
-}
-
-/**
- * Form submission handler for system_logging_settings().
- *
- * @see syslog_form_system_logging_settings_alter()
- */
-function syslog_logging_settings_submit($form, FormStateInterface $form_state) {
-  \Drupal::config('syslog.settings')
-    ->set('identity', $form_state->getValue('syslog_identity'))
-    ->set('facility', $form_state->getValue('syslog_facility'))
-    ->set('format', $form_state->getValue('syslog_format'))
-    ->save();
-}
-
-/**
- * Lists all possible syslog facilities for UNIX/Linux.
- *
- * @return array
- *   An array of syslog facilities for UNIX/Linux.
- */
-function syslog_facility_list() {
-  return array(
-    LOG_LOCAL0 => 'LOG_LOCAL0',
-    LOG_LOCAL1 => 'LOG_LOCAL1',
-    LOG_LOCAL2 => 'LOG_LOCAL2',
-    LOG_LOCAL3 => 'LOG_LOCAL3',
-    LOG_LOCAL4 => 'LOG_LOCAL4',
-    LOG_LOCAL5 => 'LOG_LOCAL5',
-    LOG_LOCAL6 => 'LOG_LOCAL6',
-    LOG_LOCAL7 => 'LOG_LOCAL7',
-  );
+  /** @var \Drupal\syslog\Form\SystemLoggingSettingsFormAlter $alter */
+  $alter = \Drupal::resolve('Drupal\syslog\Form\SystemLoggingSettingsFormAlter');
+  $alter->alter($form, $form_state);
 }