diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index c396171..32a22c4 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -540,8 +540,8 @@ protected function processExtension(array &$cache, $name, $type, $theme, $path)
   }
 
   /**
-  * This completes the theme registry adding missing functions and hooks.
-
+   * This completes the theme registry adding missing functions and hooks.
+   *
    * @param array $cache
    *   The theme registry that will eventually be cached; It is an associative
    *   array keyed by theme hooks, whose values are associative arrays
@@ -566,7 +566,7 @@ protected function processExtension(array &$cache, $name, $type, $theme, $path)
    *     definition is kept.
    *   - 'preprocess functions': See _theme() for detailed documentation.
    * @param object $theme
-   *   current active theme.
+   *   Current active theme.
   */
   protected function postProcessExtension(array &$cache, $theme) {
 
@@ -585,7 +585,8 @@ protected function postProcessExtension(array &$cache, $theme) {
     }
     $prefixes[] = $theme->getName();
 
-    // Collect all known hooks. Discovered functions must be based on a known hook.
+    // Collect all known hooks. Discovered functions must be based on a known
+    // hook.
     $hooks = implode('|', array_keys($cache));
 
     // Collect all variable processor functions in the correct order.
@@ -595,13 +596,13 @@ protected function postProcessExtension(array &$cache, $theme) {
     }
 
     // Add missing variable processors. This is needed for hooks that do not
-    // explictly register the hook. For example, when a theme contains a variable
-    // process function but it does not implement a template, it will go missing.
-    // This will add the expected function. It also allows modules or themes to
-    // have a variable process function based on a pattern even if the hook does
-    // not exist.
+    // explictly register the hook. For example, when a theme contains a
+    // variable process function but it does not implement a template, it will
+    // go missing. This will add the expected function. It also allows modules
+    // or themes to have a variable process function based on a pattern even if
+    // the hook does not exist.
     foreach ($processors as $processor) {
-      $hook  = substr($processor, strpos($processor, 'preprocess_') + strlen('preprocess_'));
+      $hook = substr($processor, strpos($processor, 'preprocess_') + strlen('preprocess_'));
       if (isset($cache[$hook]['preprocess functions']) && !in_array($hook, $cache[$hook]['preprocess functions'])) {
         // Add missing processor to existing hook.
         $cache[$hook]['preprocess functions'][] = $processor;
@@ -620,12 +621,13 @@ protected function postProcessExtension(array &$cache, $theme) {
         }
       }
     }
-    // Inherit all base hook variable processors into pattern hooks. This ensures
-    // that derivative hooks have a complete set of variable process functions.
+    // Inherit all base hook variable processors into pattern hooks.
+    // This ensures that derivative hooks have a complete set of variable
+    // process functions.
     foreach ($cache as $hook => $info) {
       // The 'base hook' is only applied to derivative hooks already registered
-      // from a pattern. This is typically set from drupal_find_theme_functions()
-      // and drupal_find_theme_templates().
+      // from a pattern. This is typically set from
+      // drupal_find_theme_functions() and drupal_find_theme_templates().
       if (isset($info['base hook']) && isset($cache[$info['base hook']]['preprocess functions'])) {
         $diff = array_diff($cache[$info['base hook']]['preprocess functions'], $info['preprocess functions']);
         $cache[$hook]['preprocess functions'] = array_merge($diff, $info['preprocess functions']);
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index 64d45e7..7eeee9d 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -99,6 +99,9 @@ function theme_test_theme_suggestions_theme_test_preprocess_suggestions($variabl
   return array('theme_test_preprocess_suggestions__' . 'suggestion');
 }
 
+/**
+ * Implements hook_preprocess_HOOK().
+ */
 function theme_test_preprocess_theme_test_preprocess_suggestions(&$variables) {
   $variables['foo'] =  'Theme hook implementor=theme_theme_test_preprocess_suggestions().';
 }