MD Downloads: remove dangling, long gone flag

chrome/test/data/webui/md_downloads/downloads_browsertest.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** @fileoverview Tests for the Material Design downloads page. */
 
 /** @const {string} Path to source root. */
 var ROOT_PATH = '../../../../../';
 
 // Polymer BrowserTest fixture.
 GEN_INCLUDE(
     [ROOT_PATH + 'chrome/test/data/webui/polymer_browser_test_base.js']);
 
 /**
  * @constructor
  * @extends {PolymerTest}
 */
 function DownloadsBrowserTest() {}
 
 DownloadsBrowserTest.prototype = {
   __proto__: PolymerTest.prototype,
 
   /** @override */
   browsePreload: 'chrome://downloads/manager.html',
 
   /** @override */
-  commandLineSwitches: [{switchName: 'enable-md-downloads'}],
-
-  /** @override */
   extraLibraries: PolymerTest.getLibraries(ROOT_PATH).concat([
     'layout_tests.js',
   ]),
 };
 
 TEST_F('DownloadsBrowserTest', 'layoutTests', function() {
   downloads.layout_tests.registerTests();
   mocha.run();
 });