diff --git a/core/core.services.yml b/core/core.services.yml
index e947b3b..2adbe7a 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1213,10 +1213,26 @@ services:
     class: Drupal\Core\StreamWrapper\ThemeStream
     tags:
       - { name: stream_wrapper, scheme: theme }
+  stream_wrapper.active_theme:
+    class: Drupal\Core\StreamWrapper\ActiveThemeStream
+    tags:
+      - { name: stream_wrapper, scheme: active-theme }
+  stream_wrapper.admin_theme:
+    class: Drupal\Core\StreamWrapper\AdminThemeStream
+    tags:
+      - { name: stream_wrapper, scheme: admin-theme }
+  stream_wrapper.default_theme:
+    class: Drupal\Core\StreamWrapper\DefaultThemeStream
+    tags:
+      - { name: stream_wrapper, scheme: default-theme }
   stream_wrapper.profile:
     class: Drupal\Core\StreamWrapper\ProfileStream
     tags:
       - { name: stream_wrapper, scheme: profile }
+  stream_wrapper.installed_profile:
+    class: Drupal\Core\StreamWrapper\InstalledProfileStream
+    tags:
+      - { name: stream_wrapper, scheme: installed-profile }
   kernel_destruct_subscriber:
     class: Drupal\Core\EventSubscriber\KernelDestructionSubscriber
     tags:
diff --git a/core/lib/Drupal/Core/StreamWrapper/ActiveThemeStream.php b/core/lib/Drupal/Core/StreamWrapper/ActiveThemeStream.php
new file mode 100644
index 0000000..5d2237c
--- /dev/null
+++ b/core/lib/Drupal/Core/StreamWrapper/ActiveThemeStream.php
@@ -0,0 +1,59 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\StreamWrapper\ActiveThemeStream.
+ */
+
+namespace Drupal\Core\StreamWrapper;
+
+/**
+ * Defines the read-only active-theme:// stream wrapper for the active theme.
+ */
+class ActiveThemeStream extends PseudoThemeStreamBase {
+
+  /**
+   * The theme negotiator service.
+   *
+   * @var \Drupal\Core\Theme\ThemeNegotiatorInterface
+   */
+  protected $themeNegotiator;
+
+  /**
+   * The route matching service.
+   *
+   * @var \Drupal\Core\Routing\RouteMatchInterface
+   */
+  protected $routeMatch;
+
+  /**
+   * Constructs a new ActiveThemeStream object.
+   */
+  public function __construct() {
+    parent::__construct();
+    $this->themeNegotiator = \Drupal::service('theme.negotiator');
+    $this->routeMatch = \Drupal::service('current_route_match');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getOwnerName() {
+    return $this->themeNegotiator->determineActiveTheme($this->routeMatch);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getName() {
+    return t('Active theme files');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return t('Local active theme files.');
+  }
+
+}
diff --git a/core/lib/Drupal/Core/StreamWrapper/AdminThemeStream.php b/core/lib/Drupal/Core/StreamWrapper/AdminThemeStream.php
new file mode 100644
index 0000000..a632c17
--- /dev/null
+++ b/core/lib/Drupal/Core/StreamWrapper/AdminThemeStream.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\StreamWrapper\AdminThemeStream.
+ */
+
+namespace Drupal\Core\StreamWrapper;
+
+/**
+ * Defines the read-only admin-theme:// stream wrapper for the active theme.
+ */
+class AdminThemeStream extends PseudoThemeStreamBase {
+
+  /**
+   * The config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * Constructs a new ActiveThemeStream object.
+   */
+  public function __construct() {
+    parent::__construct();
+    $this->configFactory = \Drupal::configFactory();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getOwnerName() {
+    return $this->configFactory->get('system.theme')->get('admin');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getName() {
+    return t('Admin theme files');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return t('Local admin theme files.');
+  }
+
+}
diff --git a/core/lib/Drupal/Core/StreamWrapper/DefaultThemeStream.php b/core/lib/Drupal/Core/StreamWrapper/DefaultThemeStream.php
new file mode 100644
index 0000000..2189f21
--- /dev/null
+++ b/core/lib/Drupal/Core/StreamWrapper/DefaultThemeStream.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\StreamWrapper\DefaultThemeStream.
+ */
+
+namespace Drupal\Core\StreamWrapper;
+
+/**
+ * Defines the read-only default-theme:// stream wrapper for the active theme.
+ */
+class DefaultThemeStream extends PseudoThemeStreamBase {
+
+  /**
+   * The theme handler service.
+   *
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected $themeHandler;
+
+  /**
+   * Constructs a new ActiveThemeStream object.
+   */
+  public function __construct() {
+    parent::__construct();
+    $this->themeHandler = \Drupal::service('theme_handler');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getOwnerName() {
+    return $this->themeHandler->getDefault();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getName() {
+    return t('Default theme files');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return t('Local default theme files.');
+  }
+
+}
diff --git a/core/lib/Drupal/Core/StreamWrapper/InstalledProfileStream.php b/core/lib/Drupal/Core/StreamWrapper/InstalledProfileStream.php
new file mode 100644
index 0000000..0302c38
--- /dev/null
+++ b/core/lib/Drupal/Core/StreamWrapper/InstalledProfileStream.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\StreamWrapper\InstalledProfileStream.
+ */
+
+namespace Drupal\Core\StreamWrapper;
+
+/**
+ * Defines the read-only installed-profile:// stream wrapper for the installed
+ * profile files.
+ */
+class InstalledProfileStream extends PseudoSystemStreamBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getOwnerName() {
+    return drupal_get_profile();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getName() {
+    return t('Current profile files');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return t('Local current profile files.');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getDirectoryPath() {
+    return dirname(drupal_get_filename('profile', $this->getOwnerName()));
+  }
+
+}
diff --git a/core/lib/Drupal/Core/StreamWrapper/ProfileStream.php b/core/lib/Drupal/Core/StreamWrapper/ProfileStream.php
index de03e6d..539ffc5 100644
--- a/core/lib/Drupal/Core/StreamWrapper/ProfileStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/ProfileStream.php
@@ -17,9 +17,6 @@ class ProfileStream extends SystemStream {
    */
   protected function getOwnerName() {
     $name = parent::getOwnerName();
-    if ($name == 'current') {
-      $name = drupal_get_profile();
-    }
 
     if (!is_null(drupal_get_filename('profile', $name))) {
       return $name;
diff --git a/core/lib/Drupal/Core/StreamWrapper/PseudoSystemStreamBase.php b/core/lib/Drupal/Core/StreamWrapper/PseudoSystemStreamBase.php
new file mode 100644
index 0000000..2ad51be
--- /dev/null
+++ b/core/lib/Drupal/Core/StreamWrapper/PseudoSystemStreamBase.php
@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\StreamWrapper\PseudoSystemStreamBase.
+ */
+
+namespace Drupal\Core\StreamWrapper;
+
+/**
+ * Defines the base class for read-only installed-profile://, active-theme://,
+ * default-theme:// and admin-theme:// stream wrappers.
+ */
+abstract class PseudoSystemStreamBase extends SystemStream {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function dirname($uri = NULL) {
+    if (!isset($uri)) {
+      $uri = $this->uri;
+    }
+
+    list($scheme) = explode('://', $uri, 2);
+    $target = $this->getTarget($uri);
+
+    $dirname = dirname($target);
+
+    if ($dirname === '.' || $dirname === '\\') {
+      $dirname = '';
+    }
+
+    return "$scheme://" . trim($dirname, '/');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getTarget($uri = NULL) {
+    if (!isset($uri)) {
+      $uri = $this->uri;
+    }
+
+    $uri_parts = explode('://', $uri, 2);
+    if (count($uri_parts) === 1) {
+      // The delimiter ('://') was not found in $uri, malformed $uri passed.
+      throw new \InvalidArgumentException(sprintf('Malformed uri parameter passed: %s', $uri));
+    }
+
+    $target = trim($uri_parts[1], '\/');
+
+    return !empty($target) ? "/$target" : '';
+  }
+
+}
diff --git a/core/lib/Drupal/Core/StreamWrapper/PseudoThemeStreamBase.php b/core/lib/Drupal/Core/StreamWrapper/PseudoThemeStreamBase.php
new file mode 100644
index 0000000..697784c
--- /dev/null
+++ b/core/lib/Drupal/Core/StreamWrapper/PseudoThemeStreamBase.php
@@ -0,0 +1,23 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\StreamWrapper\PseudoThemeStreamBase.
+ */
+
+namespace Drupal\Core\StreamWrapper;
+
+/**
+ * Defines the base class for read-only 'active-theme://', 'default-theme://'
+ * and 'admin-theme://' theme stream wrappers.
+ */
+abstract class PseudoThemeStreamBase extends PseudoSystemStreamBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getDirectoryPath() {
+    return dirname(drupal_get_filename('theme', $this->getOwnerName()));
+  }
+
+}
diff --git a/core/lib/Drupal/Core/StreamWrapper/SystemStream.php b/core/lib/Drupal/Core/StreamWrapper/SystemStream.php
index 5bb3ca5..bf064d2 100644
--- a/core/lib/Drupal/Core/StreamWrapper/SystemStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/SystemStream.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\Core\StreamWrapper;
 
-use Symfony\Component\HttpFoundation\RequestStack;
-
 /**
  * Defines a base stream wrapper implementation.
  *
diff --git a/core/lib/Drupal/Core/StreamWrapper/ThemeStream.php b/core/lib/Drupal/Core/StreamWrapper/ThemeStream.php
index 3a60f0f..d39015f 100644
--- a/core/lib/Drupal/Core/StreamWrapper/ThemeStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/ThemeStream.php
@@ -7,12 +7,6 @@
 
 namespace Drupal\Core\StreamWrapper;
 
-use Drupal\Core\Config\ConfigFactoryInterface;
-use Drupal\Core\Extension\ThemeHandlerInterface;
-use Drupal\Core\Routing\RouteMatchInterface;
-use Drupal\Core\Theme\ThemeNegotiatorInterface;
-use Symfony\Component\HttpFoundation\RequestStack;
-
 /**
  * Defines the read-only theme:// stream wrapper for theme files.
  */
@@ -26,35 +20,11 @@ class ThemeStream extends SystemStream {
   protected $themeHandler;
 
   /**
-   * The theme negotiator service.
-   *
-   * @var \Drupal\Core\Theme\ThemeNegotiatorInterface
-   */
-  protected $themeNegotiator;
-
-  /**
-   * The config factory.
-   *
-   * @var \Drupal\Core\Config\ConfigFactoryInterface
-   */
-  protected $configFactory;
-
-  /**
-   * The route matching service.
-   *
-   * @var \Drupal\Core\Routing\RouteMatchInterface
-   */
-  protected $routeMatch;
-
-  /**
    * Constructs a new ThemeStream object.
    */
   public function __construct() {
     parent::__construct();
     $this->themeHandler = \Drupal::service('theme_handler');
-    $this->themeNegotiator = \Drupal::service('theme.negotiator');
-    $this->configFactory = \Drupal::configFactory();
-    $this->routeMatch = \Drupal::service('current_route_match');
   }
 
   /**
@@ -62,17 +32,7 @@ public function __construct() {
    */
   protected function getOwnerName() {
     $name = parent::getOwnerName();
-    switch ($name) {
-      case 'current':
-        $name = $this->getActiveTheme();
-        break;
-      case 'default':
-        $name = $this->themeHandler->getDefault();
-        break;
-      case 'admin':
-        $name = $this->configFactory->get('system.theme')->get('admin');
-        break;
-    }
+
     // Return name only for installed themes.
     if ($this->themeHandler->themeExists($name)) {
       return $name;
@@ -91,16 +51,6 @@ protected function getDirectoryPath() {
   }
 
   /**
-   * Gets the currently active theme.
-   *
-   * @return string|null
-   *   Returns the active theme name, else return NULL.
-   */
-  protected function getActiveTheme() {
-    return $this->themeNegotiator->determineActiveTheme($this->routeMatch);
-  }
-
-  /**
    * {@inheritdoc}
    */
   public function getName() {
diff --git a/core/modules/system/src/Tests/File/SystemStreamTest.php b/core/modules/system/src/Tests/File/SystemStreamTest.php
index 5d4d505..94c85db 100644
--- a/core/modules/system/src/Tests/File/SystemStreamTest.php
+++ b/core/modules/system/src/Tests/File/SystemStreamTest.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\StreamWrapperInterface;
+use Drupal\Core\Theme\ActiveTheme;
 use Drupal\simpletest\KernelTestBase;
 
 /**
@@ -133,8 +134,8 @@ protected function moduleStreamTestCasesProvider($method) {
           'module://system/css',
           'module://file_test',
           'module://file_test/src',
-          [new \InvalidArgumentException(), 'Module ckeditor does not exist or is not installed'],
-          [new \InvalidArgumentException(), 'Module foo_bar does not exist or is not installed'],
+          new \InvalidArgumentException('Module ckeditor does not exist or is not installed'),
+          new \InvalidArgumentException('Module foo_bar does not exist or is not installed'),
         ]);
       case 'realpath':
         return array_combine($uris, [
@@ -142,8 +143,8 @@ protected function moduleStreamTestCasesProvider($method) {
           DRUPAL_ROOT . '/core/modules/system/css/system.admin.css',
           DRUPAL_ROOT . '/core/modules/file/tests/file_test/file_test.dummy.inc',
           DRUPAL_ROOT . '/core/modules/file/tests/file_test/src/file_test.dummy.inc',
-          [new \InvalidArgumentException(), 'Module ckeditor does not exist or is not installed'],
-          [new \InvalidArgumentException(), 'Module foo_bar does not exist or is not installed'],
+          new \InvalidArgumentException('Module ckeditor does not exist or is not installed'),
+          new \InvalidArgumentException('Module foo_bar does not exist or is not installed'),
         ]);
       case 'getExternalUrl':
         $base_url = \Drupal::request()->getUriForPath(base_path());
@@ -152,8 +153,8 @@ protected function moduleStreamTestCasesProvider($method) {
           $base_url . 'core/modules/system/css/system.admin.css',
           $base_url . 'core/modules/file/tests/file_test/file_test.dummy.inc',
           $base_url . 'core/modules/file/tests/file_test/src/file_test.dummy.inc',
-          [new \InvalidArgumentException(), 'Module ckeditor does not exist or is not installed'],
-          [new \InvalidArgumentException(), 'Module foo_bar does not exist or is not installed'],
+          new \InvalidArgumentException('Module ckeditor does not exist or is not installed'),
+          new \InvalidArgumentException('Module foo_bar does not exist or is not installed'),
         ]);
     }
   }
@@ -193,8 +194,6 @@ protected function profileStreamTestCasesProvider($method) {
       'profile://minimal/config/install/block.block.stark_login.yml',
       'profile://minimal/config/install/node.type.article.yml',
       'profile://foo_bar/',
-      'profile://current',
-      'profile://current/minimal.info.yml',
     ];
 
     switch ($method) {
@@ -203,17 +202,76 @@ protected function profileStreamTestCasesProvider($method) {
           'profile://minimal',
           'profile://minimal/config/install',
           'profile://minimal/config/install',
-          [new \InvalidArgumentException(), 'Profile foo_bar does not exist'],
-          'profile://minimal',
-          'profile://minimal',
+          new \InvalidArgumentException('Profile foo_bar does not exist'),
         ]);
       case 'realpath':
         return array_combine($uris, [
           DRUPAL_ROOT . '/core/profiles/minimal',
           DRUPAL_ROOT . '/core/profiles/minimal/config/install/block.block.stark_login.yml',
           DRUPAL_ROOT . '/core/profiles/minimal/config/install/node.type.article.yml',
-          [new \InvalidArgumentException(), 'Profile foo_bar does not exist'],
+          new \InvalidArgumentException('Profile foo_bar does not exist'),
+        ]);
+      case 'getExternalUrl':
+        $base_url = \Drupal::request()->getUriForPath(base_path());
+        return array_combine($uris, [
+          $base_url . 'core/profiles/minimal',
+          $base_url . 'core/profiles/minimal/config/install/block.block.stark_login.yml',
+          $base_url . 'core/profiles/minimal/config/install/node.type.article.yml',
+          new \InvalidArgumentException('Profile foo_bar does not exist'),
+        ]);
+    }
+  }
+
+  /**
+   * Test the installed profile stream wrapper functions.
+   */
+  public function testInstalledProfileStream() {
+    // Generate a profile stream wrapper instance.
+    $instance = $this->streamWrapperManager->getViaScheme('installed-profile');
+
+    // Test dirname().
+    $data = $this->installedProfileStreamTestCasesProvider('dirname');
+    $this->runTestOnInstanceMethod($instance, 'dirname', $data);
+
+    // Test realpath().
+    $data = $this->installedProfileStreamTestCasesProvider('realpath');
+    $this->runTestOnInstanceMethod($instance, 'realpath', $data);
+
+    // Test getExternalUrl().
+    $data = $this->installedProfileStreamTestCasesProvider('getExternalUrl');
+    $this->runTestOnInstanceMethod($instance, 'getExternalUrl', $data);
+  }
+
+  /**
+   * Provides test cases for testProfileStream().
+   *
+   * @param string $method
+   *   The method to be tested.
+   *
+   * @return array
+   *   Associative array with test cases as values, keyed by uri.
+   */
+  protected function installedProfileStreamTestCasesProvider($method) {
+    $uris = [
+      'installed-profile://',
+      'installed-profile://config/install/block.block.stark_login.yml',
+      'installed-profile://config/install/node.type.article.yml',
+      'installed-profile://minimal.info.yml',
+    ];
+
+    switch ($method) {
+      case 'dirname':
+        return array_combine($uris, [
+          'installed-profile://',
+          'installed-profile://config/install',
+          'installed-profile://config/install',
+          'installed-profile://',
+        ]);
+      case 'realpath':
+        return array_combine($uris, [
           DRUPAL_ROOT . '/core/profiles/minimal',
+          DRUPAL_ROOT . '/core/profiles/minimal/config/install/block.block.stark_login.yml',
+          DRUPAL_ROOT . '/core/profiles/minimal/config/install/node.type.article.yml',
           DRUPAL_ROOT . '/core/profiles/minimal/minimal.info.yml',
         ]);
       case 'getExternalUrl':
@@ -222,8 +280,6 @@ protected function profileStreamTestCasesProvider($method) {
           $base_url . 'core/profiles/minimal',
           $base_url . 'core/profiles/minimal/config/install/block.block.stark_login.yml',
           $base_url . 'core/profiles/minimal/config/install/node.type.article.yml',
-          [new \InvalidArgumentException(), 'Profile foo_bar does not exist'],
-          $base_url . 'core/profiles/minimal',
           $base_url . 'core/profiles/minimal/minimal.info.yml',
         ]);
     }
@@ -233,28 +289,10 @@ protected function profileStreamTestCasesProvider($method) {
    * Test the Theme stream wrapper functions.
    */
   public function testThemeStream() {
-    /** @var \Drupal\Core\Config\ConfigFactoryInterface $config_factory */
-    $config_factory = $this->container->get('config.factory');
     /** @var \Drupal\Core\Extension\ThemeInstallerInterface $theme_installer */
     $theme_installer = $this->container->get('theme_installer');
-    /** @var \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler */
-    $theme_handler = $this->container->get('theme_handler');
-
-    // Install Stark, Bartik and Seven themes.
-    $theme_installer->install(['bartik', 'seven', 'stark']);
-
-    // Set admin theme to Seven.
-    $system_theme = $config_factory->getEditable('system.theme');
-    $this->assertNull($system_theme->get('admin'));
-    $system_theme->set('admin', 'seven')->save();
-    $this->assertEqual($system_theme->get('admin'), 'seven');
-
-    // Set default theme to Bartik.
-    $theme_handler->setDefault('bartik');
-    $this->assertEqual($theme_handler->getDefault(), 'bartik');
-
-    // Uninstall Stark theme.
-    $theme_installer->uninstall(['stark']);
+    // Install Bartik and Seven themes.
+    $theme_installer->install(['bartik', 'seven']);
 
     // Generate a theme stream wrapper instance.
     $instance = $this->streamWrapperManager->getViaScheme('theme');
@@ -287,12 +325,6 @@ protected function themeStreamTestCasesProvider($method) {
       'theme://seven/style.css',
       'theme://bartik/color/preview.js',
       'theme://fifteen/screenshot.png',
-      'theme://current',
-      'theme://current/logo.png',
-      'theme://default',
-      'theme://default/bartik.info.yml',
-      'theme://admin',
-      'theme://admin/fake.info.yml',
       'theme://stark/stark.info.yml',
     ];
 
@@ -302,28 +334,16 @@ protected function themeStreamTestCasesProvider($method) {
           'theme://seven',
           'theme://seven',
           'theme://bartik/color',
-          [new \InvalidArgumentException(), 'Theme fifteen does not exist or is not installed'],
-          'theme://bartik',
-          'theme://bartik',
-          'theme://bartik',
-          'theme://bartik',
-          'theme://seven',
-          'theme://seven',
-          [new \InvalidArgumentException(), 'Theme stark does not exist or is not installed'],
+          new \InvalidArgumentException('Theme fifteen does not exist or is not installed'),
+          new \InvalidArgumentException('Theme stark does not exist or is not installed'),
         ]);
       case 'realpath':
         return array_combine($uris, [
           DRUPAL_ROOT . '/core/themes/seven',
           DRUPAL_ROOT . '/core/themes/seven/style.css',
           DRUPAL_ROOT . '/core/themes/bartik/color/preview.js',
-          [new \InvalidArgumentException(), 'Theme fifteen does not exist or is not installed'],
-          DRUPAL_ROOT . '/core/themes/bartik',
-          DRUPAL_ROOT . '/core/themes/bartik/logo.png',
-          DRUPAL_ROOT . '/core/themes/bartik',
-          DRUPAL_ROOT . '/core/themes/bartik/bartik.info.yml',
-          DRUPAL_ROOT . '/core/themes/seven',
-          DRUPAL_ROOT . '/core/themes/seven/fake.info.yml',
-          [new \InvalidArgumentException(), 'Theme stark does not exist or is not installed'],
+          new \InvalidArgumentException('Theme fifteen does not exist or is not installed'),
+          new \InvalidArgumentException('Theme stark does not exist or is not installed'),
         ]);
       case 'getExternalUrl':
         $base_url = \Drupal::request()->getUriForPath(base_path());
@@ -331,19 +351,90 @@ protected function themeStreamTestCasesProvider($method) {
           $base_url . 'core/themes/seven',
           $base_url . 'core/themes/seven/style.css',
           $base_url . 'core/themes/bartik/color/preview.js',
-          [new \InvalidArgumentException(), 'Theme fifteen does not exist or is not installed'],
+          new \InvalidArgumentException('Theme fifteen does not exist or is not installed'),
+          new \InvalidArgumentException('Theme stark does not exist or is not installed'),
+        ]);
+    }
+  }
+
+  /**
+   * Test the pseudo theme stream wrapper functions.
+   */
+  public function testPseudoThemeStreams() {
+    /** @var \Drupal\Core\Config\ConfigFactoryInterface $config_factory */
+    $config_factory = $this->container->get('config.factory');
+    /** @var \Drupal\Core\Extension\ThemeInstallerInterface $theme_installer */
+    $theme_installer = $this->container->get('theme_installer');
+
+    // Install Bartik theme.
+    $theme_installer->install(['bartik']);
+    // Set default and admin theme to Bartik.
+    $config_factory->getEditable('system.theme')
+      ->set('default', 'bartik')
+      ->set('admin', 'bartik')
+      ->save();
+
+    foreach (['active', 'default', 'admin'] as $scheme) {
+      $scheme .= '-theme';
+
+      // Generate a theme stream wrapper instance.
+      $instance = $this->streamWrapperManager->getViaScheme($scheme);
+
+      // Test dirname().
+      $data = $this->pseudoThemeStreamTestCasesProvider('dirname', $scheme);
+      $this->runTestOnInstanceMethod($instance, 'dirname', $data);
+
+      // Test realpath().
+      $data = $this->pseudoThemeStreamTestCasesProvider('realpath', $scheme);
+      $this->runTestOnInstanceMethod($instance, 'realpath', $data);
+
+      // Test getExternalUrl().
+      $data = $this->pseudoThemeStreamTestCasesProvider('getExternalUrl', $scheme);
+      $this->runTestOnInstanceMethod($instance, 'getExternalUrl', $data);
+    }
+  }
+
+  /**
+   * Provides test cases for testPseudoThemeStreams().
+   *
+   * @param string $method
+   *   The method to be tested.
+   * @param string $scheme
+   *   The scheme to be tested.
+   *
+   * @return array
+   *   Associative array with test cases as values, keyed by uri.
+   */
+  protected function pseudoThemeStreamTestCasesProvider($method, $scheme) {
+    $uris = [
+      "$scheme://",
+      "$scheme://logo.png",
+      "$scheme://color/preview.js",
+    ];
+
+    switch ($method) {
+      case 'dirname':
+        return array_combine($uris, [
+          "$scheme://",
+          "$scheme://",
+          "$scheme://color",
+        ]);
+      case 'realpath':
+        return array_combine($uris, [
+          DRUPAL_ROOT . '/core/themes/bartik',
+          DRUPAL_ROOT . '/core/themes/bartik/logo.png',
+          DRUPAL_ROOT . '/core/themes/bartik/color/preview.js',
+        ]);
+      case 'getExternalUrl':
+        $base_url = \Drupal::request()->getUriForPath(base_path());
+        return array_combine($uris, [
           $base_url . 'core/themes/bartik',
           $base_url . 'core/themes/bartik/logo.png',
-          $base_url . 'core/themes/bartik',
-          $base_url . 'core/themes/bartik/bartik.info.yml',
-          $base_url . 'core/themes/seven',
-          $base_url . 'core/themes/seven/fake.info.yml',
-          [new \InvalidArgumentException(), "Theme stark does not exist or is not installed"],
+          $base_url . 'core/themes/bartik/color/preview.js',
         ]);
     }
   }
 
-
   /**
    * Helper method to run specific tests on each StreamWrapper method.
    *
@@ -357,24 +448,25 @@ protected function themeStreamTestCasesProvider($method) {
    *   - The test result message.
    */
   private function runTestOnInstanceMethod(StreamWrapperInterface $instance, $method, array $data) {
-    foreach ($data as $uri => $info) {
+    foreach ($data as $uri => $case) {
       $instance->setUri($uri);
-      if (is_array($info)) {
-        $message = sprintf('Exception thrown: \InvalidArgumentException("%s").', $info[1]);
+      if ($case instanceof \InvalidArgumentException) {
+        /** @var \InvalidArgumentException $case */
+        $message = sprintf('Exception thrown: \InvalidArgumentException("%s").', $case->getMessage());
         try {
           $instance->$method();
           $this->fail($message);
         }
         catch (\InvalidArgumentException $e) {
-          $this->assertIdentical($e->getMessage(), $info[1], $message);
+          $this->assertIdentical($e->getMessage(), $case->getMessage(), $message);
         }
       }
-      else {
+      elseif (is_string($case)) {
         if ($method == 'realpath') {
           // realpath() returns strings with OS-specific DIRECTORY_SEPARATOR.
-          $info = str_replace('/', DIRECTORY_SEPARATOR, $info);
+          $case = str_replace('/', DIRECTORY_SEPARATOR, $case);
         }
-        $this->assertEqual($instance->$method(), $info);
+        $this->assertEqual($instance->$method(), $case);
       }
     }
   }