CWebDavTools::allowPreviewFile

static function allowPreviewFile($filePath, $fileSize, $checkFileSize = true, $service = null)
{
	return
		(!$checkFileSize || $fileSize < CWebDavExtLinks::$maxSizeForView) &&
		(in_array(ltrim($filePath, '.'), CWebDavExtLinks::$allowedExtensionsGoogleViewer) ||
		in_array(ltrim(GetFileExtension($filePath), '.'), CWebDavExtLinks::$allowedExtensionsGoogleViewer));
}