Piwik\AssetManager::compileCustomStylesheets PHP Method

    public static function compileCustomStylesheets($files)
    {
        $assetManager = new AssetManager();
        $fetcher = new StaticUIAssetFetcher($files, $priorityOrder = array(), $theme = null);
        $assetManager->setMinimalStylesheetFetcher($fetcher);
        return $assetManager->getCompiledBaseCss()->getContent();
    }

 /**
  * Return the base.less compiled to css
  *
  * @return string
  */
 public function getUpdaterCss()
 {
     Common::sendHeader('Content-Type: text/css');
     Common::sendHeader('Cache-Control: max-age=' . 60 * 60);
     $files = array('plugins/Morpheus/stylesheets/base/bootstrap.css', 'plugins/Morpheus/stylesheets/base/icons.css', 'libs/jquery/themes/base/jquery-ui.min.css', 'libs/bower_components/materialize/dist/css/materialize.min.css', 'plugins/Morpheus/stylesheets/base.less', 'plugins/Morpheus/stylesheets/general/_forms.less', 'plugins/Morpheus/stylesheets/simple_structure.css', 'plugins/CoreHome/stylesheets/jquery.ui.autocomplete.css', 'plugins/CoreUpdater/stylesheets/updateLayout.css');
     return AssetManager::compileCustomStylesheets($files);
 }