[cros] Possible fix for crash - check whether LoginPerformer instance needs to be recreated.

chrome/browser/chromeos/login/existing_user_controller.cc

 // Copyright (c) 2010 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/chromeos/login/existing_user_controller.h"
 
 #include <algorithm>
 #include <functional>
 #include <map>
 
@@ skipping 542 matching lines @@
   } else {
     // Postpone CompleteOffTheRecordLogin until registration completion.
     ActivateWizard(WizardController::kRegistrationScreenName);
   }
 }
 
 void ExistingUserController::OnPasswordChangeDetected(
     const GaiaAuthConsumer::ClientLoginResult& credentials) {
   // When signing in as a "New user" always remove old cryptohome.
   if (selected_view_index_ == controllers_.size() - 1) {
-    login_performer_->ResyncEncryptedData();
+    ResyncEncryptedData();
     return;
   }
 
   // Must not proceed without signature verification.
   bool trusted_setting_available = user_settings_->RequestTrustedOwner(
       method_factory_.NewRunnableMethod(
           &ExistingUserController::OnPasswordChangeDetected,
           credentials));
   if (!trusted_setting_available) {
     // Value of owner email is still not verified.
@@ skipping 37 matching lines @@
       break;
   }
 }
 
 void ExistingUserController::OnCaptchaEntered(const std::string& captcha) {
   login_performer_->set_captcha(captcha);
 }
 
 void ExistingUserController::RecoverEncryptedData(
     const std::string& old_password) {
-  login_performer_->RecoverEncryptedData(old_password);
+  // LoginPerformer instance has state of the user so it should exist.
+  if (login_performer_.get())
+    login_performer_->RecoverEncryptedData(old_password);
 }
 
 void ExistingUserController::ResyncEncryptedData() {
-  login_performer_->ResyncEncryptedData();
+  // LoginPerformer instance has state of the user so it should exist.
+  if (login_performer_.get())
+    login_performer_->ResyncEncryptedData();
 }
 
 }  // namespace chromeos