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

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

Index: chrome/test/data/webui/settings/site_settings_page_browsertest.js
diff --git a/chrome/test/data/webui/settings/site_settings_page_browsertest.js b/chrome/test/data/webui/settings/site_settings_page_browsertest.js
index 0b8256e20576223d11dd2861c873ae964fb31fa0..0b9ade75861c1cdb50d7ea52ea910f064733d7bc 100644
--- a/chrome/test/data/webui/settings/site_settings_page_browsertest.js
+++ b/chrome/test/data/webui/settings/site_settings_page_browsertest.js
@@ -15,7 +15,13 @@ 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;