Disable WelcomeScreenBrowserTest.SelectedLanguage

Disable the test because it's flaky on ChromeOS

Bug: 1028319
Tbr: tbarzic@chromium.org
Change-Id: I8f3abdd4ea0b2ed8cd485a31cd622e213aed4c8d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1933204Reviewed-by: Owen Min <zmin@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718873}

chrome/browser/chromeos/login/screens/welcome_screen_browsertest.cc

@@ -394,7 +394,7 @@ IN_PROC_BROWSER_TEST_F(WelcomeScreenBrowserTest, PRE_SelectedLanguage) {
             locale);
 }
 
-IN_PROC_BROWSER_TEST_F(WelcomeScreenBrowserTest, SelectedLanguage) {
+IN_PROC_BROWSER_TEST_F(WelcomeScreenBrowserTest, DISABLED_SelectedLanguage) {
   observer_->Wait();
   const std::string locale = "ru";
   EXPECT_EQ(g_browser_process->local_state()->GetString(