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

BUG=chromium-os:23458
TEST=manual


Review URL: http://codereview.chromium.org/8746012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112207 0039d316-1c4b-4281-b951-d872f2087c98

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.