Additional checks/calls for cases when WebUI may be already gone but OOBE screen instance is not

chrome/browser/chromeos/login/eula_screen.cc

 // Copyright (c) 2012 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/eula_screen.h"
 
 #include "base/logging.h"
 #include "chrome/browser/chromeos/cros/cros_library.h"
 #include "chrome/browser/chromeos/cros/cryptohome_library.h"
 #include "chrome/browser/chromeos/customization_document.h"
 #include "chrome/browser/chromeos/login/screen_observer.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
 
 namespace chromeos {
 
 EulaScreen::EulaScreen(ScreenObserver* observer, EulaScreenActor* actor)
     : WizardScreen(observer), actor_(actor), password_fetcher_(this) {
-  actor_->SetDelegate(this);
+  DCHECK(actor_);
+  if (actor_)
+    actor_->SetDelegate(this);
 }
 
 EulaScreen::~EulaScreen() {
   if (actor_)
     actor_->SetDelegate(NULL);
 }
 
 void EulaScreen::PrepareToShow() {
-  actor_->PrepareToShow();
+  if (actor_)
+    actor_->PrepareToShow();
 }
 
 void EulaScreen::Show() {
   // Command to own the TPM.
   chromeos::CrosLibrary::Get()->
       GetCryptohomeLibrary()->TpmCanAttemptOwnership();
-  actor_->Show();
+  if (actor_)
+    actor_->Show();
 }
 
 void EulaScreen::Hide() {
-  actor_->Hide();
+  if (actor_)
+    actor_->Hide();
 }
 
 std::string EulaScreen::GetName() const {
   return WizardController::kEulaScreenName;
 }
 
 bool EulaScreen::IsTpmEnabled() const {
   return chromeos::CrosLibrary::Get()->GetCryptohomeLibrary()->TpmIsEnabled();
 }
 
@@ skipping 17 matching lines @@
   get_screen_observer()->SetUsageStatisticsReporting(is_usage_stats_checked);
   get_screen_observer()->OnExit(accepted
                    ? ScreenObserver::EULA_ACCEPTED
                    : ScreenObserver::EULA_BACK);
 }
 
 void EulaScreen::InitiatePasswordFetch() {
   if (tpm_password_.empty()) {
     password_fetcher_.Fetch();
     // Will call actor after password has been fetched.
-  } else {
+  } else if (actor_) {
     actor_->OnPasswordFetched(tpm_password_);
   }
 }
 
 void EulaScreen::OnPasswordFetched(const std::string& tpm_password) {
   tpm_password_ = tpm_password;
   if (actor_)
     actor_->OnPasswordFetched(tpm_password_);
 }
 
 bool EulaScreen::IsUsageStatsEnabled() const {
   return get_screen_observer()->GetUsageStatisticsReporting();
 }
 
 void EulaScreen::OnActorDestroyed(EulaScreenActor* actor) {
   if (actor_ == actor)
     actor_ = NULL;
 }
 
 }  // namespace chromeos