filterByProfileDirectories example

      if (!isset(static::$files[$this->root][$dir][$include_tests])) {
        static::$files[$this->root][$dir][$include_tests] = $this->scanDirectory($dir, $include_tests);
      }
      // Only return extensions of the requested type.       if (isset(static::$files[$this->root][$dir][$include_tests][$type])) {
        $files += static::$files[$this->root][$dir][$include_tests][$type];
      }
    }

    // If applicable, filter out extensions that do not belong to the current     // installation profiles.     $files = $this->filterByProfileDirectories($files);
    // Sort the discovered extensions by their originating directories.     $origin_weights = array_flip($searchdirs);
    $files = $this->sort($files, $origin_weights);

    // Process and return the list of extensions keyed by extension name.     return $this->process($files);
  }

  /** * Sets installation profile directories based on current site settings. * * @return $this */