cros: Hide Discover OOBE screen for public sessions

Bug: 895031
Change-Id: Icec3aea6c9459252edf5a68ff88d9e747cffa174
Reviewed-on: https://chromium-review.googlesource.com/c/1281165Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599853}

chrome/browser/chromeos/login/wizard_controller.cc

@@ -893,6 +893,10 @@ void WizardController::ShowMultiDeviceSetupScreen() {
 }
 
 void WizardController::ShowDiscoverScreen() {
+  if (IsPublicSessionOrEphemeralLogin()) {
+    OnDiscoverScreenFinished();
+    return;
+  }
   VLOG(1) << "Showing Discover screen.";
   UpdateStatusAreaVisibilityForScreen(OobeScreen::SCREEN_DISCOVER);
   SetCurrentScreen(GetScreen(OobeScreen::SCREEN_DISCOVER));