cros: Fix Oobe.isEnrollmentSuccessfulForTest

The function checks a deleted element. I switched to checking enrollment
step.

Bug: 1042594
Test: manual call of the function in devtools
Change-Id: I3f0cdc0336bc6be431e68a798aee95d8447052a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2002513Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732607}

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

@@ -342,10 +342,13 @@ cr.define('cr.ui', function() {
    * attribute screen if it's present.
    */
   Oobe.isEnrollmentSuccessfulForTest = function() {
-    if ($('enterprise-enrollment').$$('.oauth-enroll-state-attribute-prompt'))
+    const step = $('enterprise-enrollment').currentStep_;
+    if (step === ENROLLMENT_STEP.ATTRIBUTE_PROMPT) {
       chrome.send('oauthEnrollAttributes', ['', '']);
+      return true;
+    }
 
-    return !!$('enterprise-enrollment').$$('.oauth-enroll-state-success');
+    return step === ENROLLMENT_STEP.SUCCESS;
   };
 
   /**