tasks/datadriver.js
function(callback) {
                if (tunnel || isSeleniumServerRunning) {
                    return callback(null);
                }

                grunt.log.debug('installing driver if needed');
                selenium.install(options.seleniumInstallOptions, function(err) {
                    if (err) {
                        return callback(err);
                    }

                    grunt.log.debug('driver installed');
                    callback(null);
                });
            }
function(callback) {
                if (tunnel || isSeleniumServerRunning) {
                    return callback(null);
                }

                grunt.log.debug('installing driver if needed');
                selenium.install(options.seleniumInstallOptions, function(err) {
                    if (err) {
                        return callback(err);
                    }

                    grunt.log.debug('driver installed');
                    callback(null);
                });
            }
install drivers if needed