Fixes possible NULL pointer crash.

BUG=none
TEST=Run out of the box in the debug mode, no DCHECKs should fail.

Review URL: http://codereview.chromium.org/6675041

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@79837 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 18 insertions, 5 deletions

diff --git a/chrome/browser/chromeos/login/base_login_display_host.cc b/chrome/browser/chromeos/login/base_login_display_host.cc
index 13ac0e5..935a4c5 100644
--- a/chrome/browser/chromeos/login/base_login_display_host.cc
+++ b/chrome/browser/chromeos/login/base_login_display_host.cc
@@ -104,6 +104,7 @@ void BaseLoginDisplayHost::StartWizard(
     const GURL& start_url) {
   DVLOG(1) << "Starting wizard, first_screen_name: " << first_screen_name;
   // Create and show the wizard.
+  wizard_controller_.reset();  // Only one controller in a time.
   wizard_controller_.reset(new WizardController(this, background_bounds_));
   wizard_controller_->SetCustomization(manifest);
   wizard_controller_->set_start_url(start_url);
@@ -127,6 +128,7 @@ void BaseLoginDisplayHost::StartSignInScreen() {
     WizardController::MarkDeviceRegistered();
   }
 
+  sign_in_controller_.reset();  // Only one controller in a time.
   sign_in_controller_.reset(new chromeos::ExistingUserController(this));
   ShowBackground();
   SetShutdownButtonEnabled(true);
diff --git a/chrome/browser/chromeos/login/existing_user_controller.cc b/chrome/browser/chromeos/login/existing_user_controller.cc
index 20b0518..4aa8bfa 100644
--- a/chrome/browser/chromeos/login/existing_user_controller.cc
+++ b/chrome/browser/chromeos/login/existing_user_controller.cc
@@ -66,6 +66,7 @@ ExistingUserController::ExistingUserController(LoginDisplayHost* host)
       num_login_attempts_(0),
       user_settings_(new UserCrosSettingsProvider),
       method_factory_(this) {
+  DCHECK(current_controller_ == NULL);
   current_controller_ = this;
 
   login_display_.reset(host_->CreateLoginDisplay(this));
@@ -138,8 +139,11 @@ void ExistingUserController::Observe(NotificationType type,
 // ExistingUserController, private:
 
 ExistingUserController::~ExistingUserController() {
-  DCHECK(current_controller_ != NULL);
-  current_controller_ = NULL;
+  if (current_controller_ == this) {
+    current_controller_ = NULL;
+  } else {
+    NOTREACHED() << "More than one controller are alive.";
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/chrome/browser/chromeos/login/wizard_controller.cc b/chrome/browser/chromeos/login/wizard_controller.cc
index 0bde193..7480735 100644
--- a/chrome/browser/chromeos/login/wizard_controller.cc
+++ b/chrome/browser/chromeos/login/wizard_controller.cc
@@ -245,7 +245,12 @@ WizardController::~WizardController() {
     widget_ = NULL;
   }
 
-  default_controller_ = NULL;
+  if (default_controller_ == this) {
+    default_controller_ = NULL;
+  } else {
+    NOTREACHED() << "More than one controller are alive.";
+  }
+
   chromeos::WizardAccessibilityHelper::GetInstance()->
       UnregisterNotifications();
 }
@@ -353,8 +358,10 @@ void WizardController::ShowLoginScreen() {
   host_->SetOobeProgress(chromeos::BackgroundView::SIGNIN);
   host_->StartSignInScreen();
   smooth_show_timer_.Stop();
-  widget_->Close();
-  widget_ = NULL;
+  if (widget_) {
+    widget_->Close();
+    widget_ = NULL;
+  }
   is_active_ = false;
 }