private function use_local_files( $css ) {
		preg_match_all( '/https\:.*?\.woff/', $css, $matches );

		$matches = array_shift( $matches );

		foreach ( $matches as $match ) {
			if ( 0 === strpos( $match, 'https://fonts.gstatic.com' ) ) {
				$new_url = Helper::download_font_file( $match );
				if ( $new_url ) {
					$css = str_replace( $match, $new_url, $css );
				}
			}
		}
		return $css;
	}