diff --git a/core/lib/Drupal/Core/PhpStorage/CacheStorage.php b/core/lib/Drupal/Core/PhpStorage/CacheStorage.php
index 872f9da..daf2cfb 100644
--- a/core/lib/Drupal/Core/PhpStorage/CacheStorage.php
+++ b/core/lib/Drupal/Core/PhpStorage/CacheStorage.php
@@ -11,7 +11,7 @@
 use Drupal\Core\Cache\DatabaseBackend;
 use Drupal\Core\Cache\DatabaseCacheTagsChecksum;
 use Drupal\Core\Database\Database;
-use Drupal\Core\StreamWrapper\SpecialInMemoryStream;
+use Drupal\Core\StreamWrapper\StreamWrapperForCacheStorage;
 
 /**
  * This class stores PHP classes in a cache storage keeping it opcacheable.
@@ -69,8 +69,8 @@ public function load($name) {
     // multiple times by the classloader as the container class is loaded.
     // So for better performance use the phar protocol.
     stream_wrapper_unregister('phar');
-    stream_wrapper_register('phar', 'Drupal\Core\StreamWrapper\SpecialInMemoryStream');
-    SpecialInMemoryStream::init($this, $cached->data);
+    stream_wrapper_register('phar', 'Drupal\Core\StreamWrapper\StreamWrapperForCacheStorage');
+    StreamWrapperForCacheStorage::init($this, $cached->data);
     $return = (include "phar://$name") !== FALSE;
     #var_dump(opcache_get_status(TRUE)['scripts']["phar://$name"]);
     // Restore the system wrapper.
@@ -162,7 +162,7 @@ public function listAll() {
    */
   protected function cacheBackend() {
     if (!isset($this->cacheBackend)) {
-      if (isset($this->configuration['cache_backend_factory']) && is_callable($this->configuration['cache_backend_factory'])) {
+      if (isset($this->configuration['cache_backend_factory'])) {
         $this->cacheBackend = call_user_func($this->configuration['cache_backend_factory'], $this->configuration);
       }
       else {
diff --git a/core/lib/Drupal/Core/StreamWrapper/SpecialInMemoryStream.php b/core/lib/Drupal/Core/StreamWrapper/StreamWrapperForCacheStorage.php
similarity index 51%
rename from core/lib/Drupal/Core/StreamWrapper/SpecialInMemoryStream.php
rename to core/lib/Drupal/Core/StreamWrapper/StreamWrapperForCacheStorage.php
index a69bc10..6ef53d0 100644
--- a/core/lib/Drupal/Core/StreamWrapper/SpecialInMemoryStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/StreamWrapperForCacheStorage.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\StreamWrapper\SpecialInMemoryStream.
+ * Contains \Drupal\Core\StreamWrapper\StreamWrapperForCacheStorage.
  */
 
 namespace Drupal\Core\StreamWrapper;
@@ -11,9 +11,11 @@
 /**
  * The stream wrapper for \Drupal\Core\PhpStorage\CacheStorage .
  *
- * This class is not usable as a generic stream wrapper.
+ * This class is not usable as a generic stream wrapper, it is specifically
+ * written to work with \Drupal\Core\PhpStorage\CacheStorage and allows us
+ * to manually set the mtime of the "file" the stream is wrapping.
  */
-class SpecialInMemoryStream {
+class StreamWrapperForCacheStorage {
 
   /**
    * @var \Drupal\Core\PhpStorage\CacheStorage
@@ -53,38 +55,6 @@ public static function init(CacheStorage $storage, $mtime) {
     static::$mtime = $mtime;
   }
 
-  public function dir_closedir() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function dir_opendir($path) {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function dir_readdir() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function dir_rewinddir() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function mkdir() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function rename() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function rmdir() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function stream_cast() {
-    return static::$handle ? static::$handle : FALSE;
-  }
-
   public function stream_close () {
     return fclose(static::$handle);
   }
@@ -97,14 +67,6 @@ public function stream_flush() {
     return fflush(static::$handle);
   }
 
-  public function stream_lock($operation) {
-    return flock(static::$handle, $operation);
-  }
-
-  public function stream_metadata() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
   public function stream_open($path) {
     static::$handle = static::$storage->open($path);
     return (bool) static::$handle;
@@ -114,34 +76,10 @@ public function stream_read($count) {
     return fread(static::$handle, $count);
   }
 
-  public function stream_seek($offset, $whence = SEEK_SET) {
-    return fseek(static::$handle, $offset, $whence);
-  }
-
-  public function stream_set_option() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
   public function stream_stat() {
     return fstat(static::$handle);
   }
 
-  public function stream_tell() {
-    return ftell(static::$handle);
-  }
-
-  public function stream_truncate() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function stream_write() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
-  public function unlink() {
-    throw new \BadMethodCallException('Not implemented');
-  }
-
   public function url_stat() {
     $return = [
       'dev' => 0,