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

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

Index: chrome/test/data/webui/settings/settings_subpage_browsertest.js
diff --git a/chrome/test/data/webui/settings/settings_subpage_browsertest.js b/chrome/test/data/webui/settings/settings_subpage_browsertest.js
index bbc22ecfc5e49f603c91c6b276c05f2935a1bd5b..5b9064973cd91322db36df350b86ad1405ff8232 100644
--- a/chrome/test/data/webui/settings/settings_subpage_browsertest.js
+++ b/chrome/test/data/webui/settings/settings_subpage_browsertest.js
@@ -96,7 +96,13 @@ SettingsBasicSubPageBrowserTest.prototype = {
   __proto__: SettingsSubPageBrowserTest.prototype,
 };
 
-TEST_F('SettingsBasicSubPageBrowserTest', 'SubPages', function() {
+// Failing on ChromiumOS dbg. https://crbug.com/709442
+GEN('#if defined(OS_CHROMEOS) && !defined(NDEBUG)');
+GEN('#define MAYBE_SubPages DISABLED_SubPages');
+GEN('#else');
+GEN('#define MAYBE_SubPages SubPages');
+GEN('#endif');
+TEST_F('SettingsBasicSubPageBrowserTest', 'MAYBE_SubPages', function() {
   suiteSetup(this.verifySubPagesHidden_.bind(this));
   suite('Basic', this.testSubPages.bind(this));
   mocha.run();