reverted:
--- b/core/lib/Drupal/Core/CoreBundle.php
+++ a/core/lib/Drupal/Core/CoreBundle.php
@@ -62,17 +62,12 @@
     // Add the compiler pass that will process the tagged services.
     $container->addCompilerPass(new RegisterPathProcessorsPass());
     $container->addCompilerPass(new ListCacheBinsPass());
-    // Add the compiler pass that will process the tagged services.
-    $container->addCompilerPass(new RegisterPathProcessorsPass());
-    $container->addCompilerPass(new ListCacheBinsPass());
   }
 
   /**
    * Registers the module handler.
    *
    * As this is different during install, it needs to stay in PHP.
-   *
-   * As this is different during install, it needs to stay in PHP.
    */
   protected function registerModuleHandler(ContainerBuilder $container) {
     // The ModuleHandler manages enabled modules and provides the ability to
diff -u b/core/modules/config/config.admin.inc b/core/modules/config/config.admin.inc
--- b/core/modules/config/config.admin.inc
+++ b/core/modules/config/config.admin.inc
@@ -38,6 +38,7 @@
     $form['no_changes'] = array(
       '#markup' => t('There are no configuration changes.'),
     );
+    $form['actions']['#access'] = FALSE;
     return $form;
   }
 
@@ -132,6 +133,14 @@
       Drupal::service('config.importer')->import();
       drupal_flush_all_caches();
       drupal_set_message(t('The configuration was imported successfully.'));
+
+      // Once a sync completes, we empty the staging directory. This prevents
+      // changes from being accidentally overwritten by stray files getting
+      // imported later.
+      $source_storage = Drupal::service('config.importer')->getSourceStorage();
+      foreach ($source_storage->listAll() as $name) {
+        $source_storage->delete($name);
+      }
     }
     catch (ConfigException $e) {
       // Return a negative result for UI purposes. We do not differentiate between
only in patch2:
unchanged:
--- a/core/modules/field/lib/Drupal/field/Tests/FieldUnitTestBase.php
+++ b/core/modules/field/lib/Drupal/field/Tests/FieldUnitTestBase.php
@@ -38,8 +38,8 @@ function setUp() {
     $this->installSchema('entity_test', 'entity_test');
     $this->installSchema('field_test', array('test_entity', 'test_entity_revision', 'test_entity_bundle'));
 
-    // Set default storage backend.
-    $this->installConfig(array('field'));
+    // Set default storage backend and configure the theme system.
+    $this->installConfig(array('field', 'system'));
   }
 
   /**
only in patch2:
unchanged:
--- a/core/modules/text/lib/Drupal/text/Tests/Formatter/TextPlainUnitTest.php
+++ b/core/modules/text/lib/Drupal/text/Tests/Formatter/TextPlainUnitTest.php
@@ -25,7 +25,7 @@ class TextPlainUnitTest extends DrupalUnitTestBase {
    *
    * @var array
    */
-  public static $modules = array('entity', 'field', 'field_sql_storage', 'text', 'field_test');
+  public static $modules = array('system', 'entity', 'field', 'field_sql_storage', 'text', 'field_test');
 
   /**
    * Contains rendered content.
@@ -45,7 +45,8 @@ public static function getInfo() {
   function setUp() {
     parent::setUp();
 
-    $this->installConfig(array('field'));
+    // Configure the theme system.
+    $this->installConfig(array('system', 'field'));
 
     // @todo Add helper methods for all of the following.