[WebUI] Disable 3 flaky tests on ChromiumOS dbg (timeouts)

chrome/test/data/webui/settings/site_settings_page_browsertest.js

 // Copyright 2017 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 Site settings page tests. */
 
 GEN_INCLUDE(['settings_page_browsertest.js']);
 /**
  * @constructor
  * @extends {SettingsPageBrowserTest}
  */
 function SettingsSiteSettingsPageBrowserTest() {}
 
 SettingsSiteSettingsPageBrowserTest.prototype = {
   __proto__: SettingsPageBrowserTest.prototype,
 };
 
-TEST_F('SettingsSiteSettingsPageBrowserTest', 'labels', function() {
+// Failing on ChromiumOS dbg. https://crbug.com/709442
+GEN('#if defined(OS_CHROMEOS) && !defined(NDEBUG)');
+GEN('#define MAYBE_labels DISABLED_labels');
+GEN('#else');
+GEN('#define MAYBE_labels labels');
+GEN('#endif');
+TEST_F('SettingsSiteSettingsPageBrowserTest', 'MAYBE_labels', function() {
   suite('Site settings page', function() {
     var ui;
 
     suiteSetup(function() {
       ui = assert(document.createElement('settings-site-settings-page'));
     });
 
     test('defaultSettingLabel_ tests', function() {
       assertEquals('a', ui.defaultSettingLabel_(
           settings.PermissionValues.ALLOW, 'a', 'b'));
       assertEquals('b', ui.defaultSettingLabel_(
           settings.PermissionValues.BLOCK, 'a', 'b'));
       assertEquals('a', ui.defaultSettingLabel_(
           settings.PermissionValues.ALLOW, 'a', 'b', 'c'));
       assertEquals('b', ui.defaultSettingLabel_(
           settings.PermissionValues.BLOCK, 'a', 'b', 'c'));
       assertEquals('c', ui.defaultSettingLabel_(
           settings.PermissionValues.SESSION_ONLY, 'a', 'b', 'c'));
       assertEquals('c', ui.defaultSettingLabel_(
           settings.PermissionValues.DEFAULT, 'a', 'b', 'c'));
       assertEquals('c', ui.defaultSettingLabel_(
           settings.PermissionValues.ASK, 'a', 'b', 'c'));
       assertEquals('c', ui.defaultSettingLabel_(
           settings.PermissionValues.DETECT_IMPORTANT_CONTENT, 'a', 'b', 'c'));
     });
   });
 
   mocha.run();
 });