[cros,login] Correctly handle situation when screens are switched very quickly.

chrome/browser/resources/chromeos/login/display_manager.js

Index: chrome/browser/resources/chromeos/login/display_manager.js
diff --git a/chrome/browser/resources/chromeos/login/display_manager.js b/chrome/browser/resources/chromeos/login/display_manager.js
index 1be90d4f5210efd9c5dd7992ad9fb6f17bf942f7..0b7939ad1368132ec40e9f383ad3c588d99fc4f9 100644
--- a/chrome/browser/resources/chromeos/login/display_manager.js
+++ b/chrome/browser/resources/chromeos/login/display_manager.js
@@ -151,7 +151,11 @@ cr.define('cr.ui.login', function() {
           !oldStep.classList.contains('hidden')) {
         oldStep.addEventListener('webkitTransitionEnd', function f(e) {
           oldStep.removeEventListener('webkitTransitionEnd', f);
-          oldStep.classList.add('hidden');
+          if (oldStep.classList.contains('faded') ||
+              oldStep.classList.contains('left') ||
+              oldStep.classList.contains('right')) {
+            oldStep.classList.add('hidden');
+          }
         });
       } else {
         // First screen on OOBE launch.