diff --git a/core/modules/editor/editor.libraries.yml b/core/modules/editor/editor.libraries.yml
index d59d259fd26..6c4b34f6cde 100644
--- a/core/modules/editor/editor.libraries.yml
+++ b/core/modules/editor/editor.libraries.yml
@@ -11,9 +11,6 @@ drupal.editor:
   version: VERSION
   js:
     js/editor.js: {}
-  css:
-    component:
-      css/editor.css: {}
   dependencies:
     - core/jquery
     - core/drupal
diff --git a/core/modules/file/file.libraries.yml b/core/modules/file/file.libraries.yml
index f72a2eb6156..ccc0c3b95a6 100644
--- a/core/modules/file/file.libraries.yml
+++ b/core/modules/file/file.libraries.yml
@@ -5,8 +5,6 @@ drupal.file:
   css:
     theme:
       css/file.admin.css: {}
-    component:
-      css/file.theme.css: {}
   dependencies:
     - core/jquery
     - core/jquery.once
diff --git a/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php b/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
new file mode 100644
index 00000000000..7cdd8750a18
--- /dev/null
+++ b/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
@@ -0,0 +1,200 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Asset\ResolvedLibraryDefinitionsFilesMatchTest.
+ */
+
+namespace Drupal\system\Tests\Asset;
+
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests that the asset files for all core libraries exist.
+ *
+ * This test also changes the active theme to each core theme to verify
+ * the libraries after theme-level libraries-override and libraries-extend are
+ * applied.
+ *
+ * @group Asset
+ */
+class ResolvedLibraryDefinitionsFilesMatchTest extends KernelTestBase {
+
+  /**
+   * The theme handler.
+   *
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected $themeHandler;
+
+  /**
+   * The theme initialization.
+   *
+   * @var \Drupal\Core\Theme\ThemeInitializationInterface
+   */
+  protected $themeInitialization;
+
+  /**
+   * The theme manager.
+   *
+   * @var \Drupal\Core\Theme\ThemeManagerInterface
+   */
+  protected $themeManager;
+
+  /**
+   * The library discovery service.
+   *
+   * @var \Drupal\Core\Asset\LibraryDiscoveryInterface
+   */
+  protected $libraryDiscovery;
+
+  /**
+   * A list of all core modules.
+   *
+   * @var string[]
+   */
+  protected $allModules;
+
+  /**
+   * A list of all core themes.
+   *
+   * We hardcode this because test themes don't use a 'package' or 'hidden' key
+   * so we don't have a good way of filtering to only get "real" themes.
+   *
+   * @var string[]
+   */
+  protected $allThemes = [
+    'bartik',
+    'classy',
+    'seven',
+    'stable',
+    'stark',
+  ];
+
+  /**
+   * A list of libraries to skip checking, in the format extension/library_name.
+   *
+   * @var string[]
+   */
+  protected $librariesToSkip = [
+    // Locale has a "dummy" library that does not actually exist.
+    'locale/translations',
+  ];
+
+  /**
+   * A list of all paths that have been checked.
+   *
+   * @var array[]
+   */
+  protected $pathsChecked;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+
+    $this->themeHandler = $this->container->get('theme_handler');
+    $this->themeInitialization = $this->container->get('theme.initialization');
+    $this->themeManager = $this->container->get('theme.manager');
+    $this->libraryDiscovery = $this->container->get('library.discovery');
+
+    // Install all core themes.
+    sort($this->allThemes);
+    $this->container->get('theme_installer')->install($this->allThemes);
+
+    // Enable all core modules.
+    $all_modules = system_rebuild_module_data();
+    $all_modules = array_filter($all_modules, function ($module) {
+      // Filter contrib, hidden, already enabled modules and modules in the
+      // Testing package.
+      if ($module->origin !== 'core' || !empty($module->info['hidden']) || $module->status == TRUE || $module->info['package'] == 'Testing') {
+        return FALSE;
+      }
+      return TRUE;
+    });
+    $this->allModules = array_keys($all_modules);
+    sort($this->allModules);
+    $this->enableModules($this->allModules);
+  }
+
+  /**
+   * Ensures that all core module and theme library files exist.
+   */
+  public function testCoreLibraryCompleteness() {
+    // First verify all libraries with no active theme.
+    $this->verifyLibraryFilesExist($this->getAllLibraries());
+
+    // Then verify all libraries for each core theme. This may seem like
+    // overkill but themes can override and extend other extensions' libraries
+    // and these changes are only applied for the active theme.
+    foreach ($this->allThemes as $theme) {
+      $this->themeManager->setActiveTheme($this->themeInitialization->getActiveThemeByName($theme));
+      $this->libraryDiscovery->clearCachedDefinitions();
+
+      $this->verifyLibraryFilesExist($this->getAllLibraries());
+    }
+  }
+
+  /**
+   * Checks that all the library files exist.
+   *
+   * @param array[]
+   *   An array of library definitions, keyed by extension, then by library, and
+   *   so on.
+   */
+  protected function verifyLibraryFilesExist($library_definitions) {
+    $root = \Drupal::root();
+    foreach ($library_definitions as $extension => $libraries) {
+      foreach ($libraries as $library_name => $library) {
+        if (in_array("$extension/$library_name", $this->librariesToSkip)) {
+          continue;
+        }
+
+        // Check that all the assets exist.
+        foreach (['css', 'js'] as $asset_type) {
+          foreach ($library[$asset_type] as $asset) {
+            $file = $asset['data'];
+            $path = $root . '/' . $file;
+            // Only check and assert each file path once.
+            if (!isset($this->pathsChecked[$path])) {
+              $this->assertTrue(is_file($path), "$file file referenced from the $extension/$library_name library exists.");
+              $this->pathsChecked[$path] = TRUE;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Gets all libraries for core and all installed modules.
+   *
+   * @return \Drupal\Core\Extension\Extension[]
+   */
+  protected function getAllLibraries() {
+    $modules = \Drupal::moduleHandler()->getModuleList();
+    $extensions = $modules;
+    $module_list = array_keys($modules);
+    sort($module_list);
+    $this->assertEqual($this->allModules, $module_list, 'All core modules are installed.');
+
+    $themes = $this->themeHandler->listInfo();
+    $extensions += $themes;
+    $theme_list = array_keys($themes);
+    sort($theme_list);
+    $this->assertEqual($this->allThemes, $theme_list, 'All core themes are installed.');
+
+    $libraries['core'] = $this->libraryDiscovery->getLibrariesByExtension('core');
+
+    $root = \Drupal::root();
+    foreach ($extensions as $extension_name => $extension) {
+      $library_file = $extension->getPath() . '/' . $extension_name . '.libraries.yml';
+      if (is_file($root . '/' . $library_file)) {
+        $libraries[$extension_name] = $this->libraryDiscovery->getLibrariesByExtension($extension_name);
+      }
+    }
+    return $libraries;
+  }
+
+}
diff --git a/core/themes/classy/classy.info.yml b/core/themes/classy/classy.info.yml
index fb5cb3e29ee..2b7705b10e8 100644
--- a/core/themes/classy/classy.info.yml
+++ b/core/themes/classy/classy.info.yml
@@ -17,3 +17,5 @@ libraries-extend:
     - classy/dropbutton
   core/drupal.dialog:
     - classy/dialog
+  file/drupal.file:
+    - classy/file