diff --git a/core/lib/Drupal/Core/Cache/CacheBackendPass.php b/core/lib/Drupal/Core/Cache/CacheBackendPass.php
index c907c930b7..21117d39fd 100644
--- a/core/lib/Drupal/Core/Cache/CacheBackendPass.php
+++ b/core/lib/Drupal/Core/Cache/CacheBackendPass.php
@@ -6,6 +6,7 @@
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 
 /**
+ * Container pass to provide a BC layer for cache backends automatically.
  */
 class CacheBackendPass implements CompilerPassInterface {
 
diff --git a/core/lib/Drupal/Core/Cache/CacheFactory.php b/core/lib/Drupal/Core/Cache/CacheFactory.php
index 9440352ae1..a6e45bb0f9 100644
--- a/core/lib/Drupal/Core/Cache/CacheFactory.php
+++ b/core/lib/Drupal/Core/Cache/CacheFactory.php
@@ -34,6 +34,8 @@ class CacheFactory implements CacheFactoryInterface, ContainerAwareInterface {
   protected $defaultBinBackends;
 
   /**
+   * A list of cache backends without a BC layer.
+   *
    * @var string[]
    */
   protected $cacheBackendsWithNonLegacy;
@@ -47,7 +49,7 @@ class CacheFactory implements CacheFactoryInterface, ContainerAwareInterface {
    *   (optional) A mapping of bin to backend service name. Mappings in
    *   $settings take precedence over this.
    * @param array $cache_backends_non_legacy
-   *   (optional)
+   *   (optional) A list of cache backends without a BC layer.
    */
   public function __construct(Settings $settings, array $default_bin_backends = [], array $cache_backends_non_legacy = []) {
     $this->settings = $settings;
diff --git a/core/lib/Drupal/Core/Cache/CacheItem.php b/core/lib/Drupal/Core/Cache/CacheItem.php
index e0fcb86253..e018feeb43 100644
--- a/core/lib/Drupal/Core/Cache/CacheItem.php
+++ b/core/lib/Drupal/Core/Cache/CacheItem.php
@@ -131,9 +131,7 @@ public function isExpired() {
     if (CacheBackendInterface::CACHE_PERMANENT === $this->expire) {
       return FALSE;
     }
-    else {
-      return \Drupal::time()->getCurrentTime() >= $this->expire;
-    }
+    return \Drupal::time()->getCurrentTime() >= $this->expire;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Cache/CacheItemCacheBackendDecorator.php b/core/lib/Drupal/Core/Cache/CacheItemCacheBackendDecorator.php
index d8da929d77..7838ce3c8d 100644
--- a/core/lib/Drupal/Core/Cache/CacheItemCacheBackendDecorator.php
+++ b/core/lib/Drupal/Core/Cache/CacheItemCacheBackendDecorator.php
@@ -2,9 +2,14 @@
 
 namespace Drupal\Core\Cache;
 
+/**
+ * Decorates a cache backend to ensure it always returns CachItem objects.
+ */
 class CacheItemCacheBackendDecorator implements CacheBackendInterface {
 
   /**
+   * The wrapped cache backend.
+   *
    * @var \Drupal\Core\Cache\CacheBackendInterface
    */
   protected $cacheBackend;
@@ -16,6 +21,16 @@ public function __construct(CacheBackendInterface $cacheBackend) {
     $this->cacheBackend = $cacheBackend;
   }
 
+  /**
+   * Wraps a cache result inside a CacheItem.
+   *
+   * @param string $cid
+   *   The cache ID.
+   * @param \stdClass|\Drupal\Core\Cache\CacheItem $result
+   *   The cache result
+   *
+   * @return \Drupal\Core\Cache\CacheItem|FALSE
+   */
   protected function wrapResult($cid, $result) {
     if ($result instanceof CacheItem) {
       return $result;
@@ -24,6 +39,8 @@ protected function wrapResult($cid, $result) {
     if ($result) {
       return new CacheItem($cid, $result->data, $result->expire, $result->tags, $result->created, $result->valid);
     }
+
+    return FALSE;
   }
 
   /**
@@ -49,69 +66,69 @@ public function getMultiple(&$cids, $allow_invalid = FALSE) {
    * {@inheritdoc}
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
-    return $this->cacheBackend->set($cid, $data, $expire, $tags);
+    $this->cacheBackend->set($cid, $data, $expire, $tags);
   }
 
   /**
    * {@inheritdoc}
    */
   public function setMultiple(array $items) {
-    return $this->cacheBackend->setMultiple($items);
+    $this->cacheBackend->setMultiple($items);
   }
 
   /**
    * {@inheritdoc}
    */
   public function delete($cid) {
-    return $this->cacheBackend->delete($cid);
+    $this->cacheBackend->delete($cid);
   }
 
   /**
    * {@inheritdoc}
    */
   public function deleteMultiple(array $cids) {
-    return $this->cacheBackend->deleteMultiple($cids);
+    $this->cacheBackend->deleteMultiple($cids);
   }
 
   /**
    * {@inheritdoc}
    */
   public function deleteAll() {
-    return $this->cacheBackend->deleteAll();
+    $this->cacheBackend->deleteAll();
   }
 
   /**
    * {@inheritdoc}
    */
   public function invalidate($cid) {
-    return $this->cacheBackend->invalidate($cid);
+    $this->cacheBackend->invalidate($cid);
   }
 
   /**
    * {@inheritdoc}
    */
   public function invalidateMultiple(array $cids) {
-    return $this->cacheBackend->invalidateMultiple($cids);
+    $this->cacheBackend->invalidateMultiple($cids);
   }
 
   /**
    * {@inheritdoc}
    */
   public function invalidateAll() {
-    return $this->cacheBackend->invalidateAll();
+    $this->cacheBackend->invalidateAll();
   }
 
   /**
    * {@inheritdoc}
    */
   public function garbageCollection() {
-    return $this->cacheBackend->garbageCollection();
+    $this->cacheBackend->garbageCollection();
   }
   /**
    * {@inheritdoc}
    */
   public function removeBin() {
-    return $this->cacheBackend->removeBin();
+    $this->cacheBackend->removeBin();
   }
 
   /**
@@ -125,7 +142,7 @@ public function __get($name) {
    * {@inheritdoc}
    */
   public function __set($name, $value) {
-    return $this->cacheBackend->{$name} = $value;
+    $this->cacheBackend->{$name} = $value;
   }
 
   /**
@@ -135,4 +152,10 @@ public function __isset($name) {
     return isset($this->cacheBackend->{$name});
   }
 
+  public function reset() {
+    if (method_exists($this->cacheBackend, 'reset')) {
+      $this->cacheBackend->reset();
+    }
+  }
+
 }