Add missing call to SetUpOnMainThread to fix test crash

This test is flaky on my machine without this patch.

Separated from issue 270563002.

BUG=
TEST=LoginStateNotificationBlockerChromeOSBrowserTest
TBR=mukai@chromium.org

Review URL: https://codereview.chromium.org/284323003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270969 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/notifications/login_state_notification_blocker_chromeos_browsertest.cc

@@ -39,6 +39,7 @@ class LoginStateNotificationBlockerChromeOSBrowserTest
 
   virtual void SetUpOnMainThread() OVERRIDE {
     chromeos::LoginState::Get()->set_always_logged_in(false);
+    chromeos::LoginManagerTest::SetUpOnMainThread();
   }
 
   virtual void CleanUpOnMainThread() OVERRIDE {