Disable OAuth2Test.MergeSession

Test is flaky. See bug for details.

NOTRY=true
TBR=nkostylev@chromium.org
BUG=408867

Review URL: https://codereview.chromium.org/522453004

Cr-Commit-Position: refs/heads/master@{#292528}

chrome/browser/chromeos/login/signin/oauth2_browsertest.cc

@@ -453,7 +453,8 @@ IN_PROC_BROWSER_TEST_F(OAuth2Test, PRE_MergeSession) {
 // MergeSession test is attempting to merge session for an existing profile
 // that was generated in PRE_PRE_MergeSession test. This attempt should fail
 // since FakeGaia instance isn't configured to return relevant tokens/cookies.
-IN_PROC_BROWSER_TEST_F(OAuth2Test, MergeSession) {
+// This test is flaky, see: crbug.com/408867.
+IN_PROC_BROWSER_TEST_F(OAuth2Test, DISABLED_MergeSession) {
   SimulateNetworkOnline();
 
   content::WindowedNotificationObserver(