diff --git a/core/lib/Drupal/Core/Extension/ExtensionList.php b/core/lib/Drupal/Core/Extension/ExtensionList.php
index a7cc21d..e50cda5 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionList.php
@@ -377,11 +377,9 @@ public function getAllInstalledInfo() {
    *   An array of arrays of .info.yml entries keyed by the extension name.
    */
   protected function recalculateInfo() {
-    $info = [];
-    foreach ($this->listExtensions() as $extension_name => $extension) {
-      $info[$extension_name] = $extension->info;
-    }
-    return $info;
+    return array_map(function (Extension $extension) {
+      return $extension->info;
+    }, $this->listExtensions());
   }
 
   /**
@@ -420,13 +418,12 @@ public function getFilenames() {
    *   An array of .info.yml file locations keyed by the extension name.
    */
   protected function recalculateFilenames() {
-    $file_names = [];
     $extensions = $this->listExtensions();
     ksort($extensions);
-    foreach ($extensions as $name => $extension) {
-      $file_names[$name] = $extension->getPathname();
-    }
-    return $file_names;
+
+    return array_map(function (Extension $extension) {
+      return $extension->getPathname();
+    }, $extensions);
   }
 
   /**
@@ -443,6 +440,8 @@ protected function recalculateFilenames() {
    * @param string $filename
    *   The filename of the extension which is to be set explicitly rather
    *   than by consulting the dynamic extension listing.
+   *
+   * @internal
    */
   public function setFilename($extension_name, $filename) {
     $this->addedFileNames[$extension_name] = $filename;
@@ -457,14 +456,14 @@ public function setFilename($extension_name, $filename) {
    * This function plays a key role in allowing Drupal's extensions (modules,
    * themes, profiles, theme_engines, etc.) to be located in different places
    * depending on a site's configuration. For example, a module 'foo' may
-   * legally be located in any of these three places:
+   * legally be located in any of these four places:
    *
    * core/modules/foo/foo.info.yml
    * modules/foo/foo.info.yml
    * sites/all/modules/foo/foo.info.yml
    * sites/example.com/modules/foo/foo.info.yml
    *
-   * while a theme 'bar' may be located in any of similar places:
+   * while a theme 'bar' may be located in any of the following four places:
    *
    * core/themes/bar/bar.info.yml
    * themes/bar/bar.info.yml
@@ -513,4 +512,14 @@ public function getPath($extension_name) {
     return dirname($this->getFilename($extension_name));
   }
 
+  /**
+   * Wraps drupal_get_profile().
+   *
+   * @todo Replace drupal_get_profile() once
+   *   https://www.drupal.org/node/2156401 is in.
+   */
+  protected function getProfile() {
+    return drupal_get_profile();
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
index b09a67b..e154c8b 100644
--- a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
@@ -87,10 +87,11 @@ protected function getExtensionDiscovery() {
    * Gets the processed active profile object, or null.
    *
    * @return \Drupal\Core\Extension\Extension|null
+   *   The active profile, if there is one.
    */
   protected function getActiveProfile() {
     $profiles = $this->profileList->listExtensions();
-    $active_profile_name = drupal_get_profile();
+    $active_profile_name = $this->getProfile();
     if ($active_profile_name && isset($profiles[$active_profile_name])) {
       return $profiles[$active_profile_name];
     }
@@ -108,9 +109,7 @@ protected function doScanExtensions() {
     $profiles = $profile_extension_discovery->scan('profile');
     // Modify the active profile object that was previously added to the module
     // list.
-    // @todo Replace drupal_get_profile() once
-    //   https://www.drupal.org/node/2156401 is in.
-    $active_profile_name = drupal_get_profile();
+    $active_profile_name = $this->getProfile();
     if ($active_profile_name && isset($profiles[$active_profile_name])) {
       $extensions[$active_profile_name] = $active_profile = $profiles[$active_profile_name];
       $active_profile = $extensions[$active_profile_name];
diff --git a/core/lib/Drupal/Core/Extension/ProfileExtensionList.php b/core/lib/Drupal/Core/Extension/ProfileExtensionList.php
index 7c3ecb3..a6bf443 100644
--- a/core/lib/Drupal/Core/Extension/ProfileExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ProfileExtensionList.php
@@ -22,7 +22,7 @@ class ProfileExtensionList extends ExtensionList {
    * {@inheritdoc}
    */
   protected function getInstalledExtensionsNames() {
-    return [drupal_get_profile()];
+    return [$this->getProfile()];
   }
 
 }