Handle a non-existing promise when receiving a signin error in the SupervisedUserListData.

chrome/browser/ui/webui/options/manage_profile_browsertest.js

Index: chrome/browser/ui/webui/options/manage_profile_browsertest.js
diff --git a/chrome/browser/ui/webui/options/manage_profile_browsertest.js b/chrome/browser/ui/webui/options/manage_profile_browsertest.js
index a0d2301cf1bfa11c713ae46723120edd1bc78ed5..4e0cca55dcf3533928702f19f220e260f0d15b4e 100644
--- a/chrome/browser/ui/webui/options/manage_profile_browsertest.js
+++ b/chrome/browser/ui/webui/options/manage_profile_browsertest.js
@@ -341,14 +341,7 @@ TEST_F('ManageProfileUITest', 'NoCreateConfirmationOnError', function() {
 });
 
 // The name and email should be inserted into the confirmation dialog.
-// Disbaled because of flakiness on Mac: crbug.com/405709
-GEN('#if defined(OS_MACOSX)');
-GEN('#define MAYBE_CreateConfirmationText \\');
-GEN('    DISABLED_CreateConfirmationText');
-GEN('#else');
-GEN('#define MAYBE_CreateConfirmationText CreateConfirmationText');
-GEN('#endif');
-TEST_F('ManageProfileUITest', 'MAYBE_CreateConfirmationText', function() {
+TEST_F('ManageProfileUITest', 'CreateConfirmationText', function() {
   var self = this;
   var custodianEmail = 'foo@example.com';