MD User Manager: Error message if pref doesn't allow creating supervised user.

chrome/browser/ui/webui/signin/signin_create_profile_handler_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/signin/signin_create_profile_handler.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/prefs/browser_prefs.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_attributes_entry.h"
@@ skipping 562 matching lines @@
   base::ListValue list_args;
   list_args.Clear();
   list_args.AppendString(kSupervisedUsername1);
   list_args.AppendString(profiles::GetDefaultAvatarIconUrl(0));
   list_args.AppendBoolean(false);  // create_shortcut
   list_args.AppendBoolean(true);  // is_supervised
   list_args.AppendString("");  // supervised_user_id
   list_args.AppendString(custodian()->GetPath().value());
   handler()->CreateProfile(&list_args);
 
-  // Expect nothing to happen.
-  EXPECT_EQ(0U, web_ui()->call_data().size());
+  // Expect a JS callbacks containing an error message.
+  EXPECT_EQ(1U, web_ui()->call_data().size());
+
+  EXPECT_EQ(kTestWebUIResponse, web_ui()->call_data()[0]->function_name());
+
+  std::string callback_name;
+  ASSERT_TRUE(web_ui()->call_data()[0]->arg1()->GetAsString(&callback_name));
+  EXPECT_EQ("create-profile-error", callback_name);
+
+  base::string16 expected_error_message = l10n_util::GetStringUTF16(
+      IDS_PROFILES_CREATE_SUPERVISED_NOT_ALLOWED_BY_POLICY);
+  base::string16 error_message;
+  ASSERT_TRUE(web_ui()->call_data()[0]->arg2()->GetAsString(&error_message));
+  EXPECT_EQ(expected_error_message, error_message);
 }