OOBE: Make UserSessionManager more robust to shutdown during the login

* Use AsWeakPtr instead of base::Unretained in the WizardController
* Check chrome::IsAttemptingShutdown together with
browser_shutdown::IsTryingToQuit. IsAttemptingShutdown covers call to
chrome::AttemptUserExit() which is common in the Chrome OS login/policy
code.

Bug: 1132397
Change-Id: I6c0e28138918a998c94f82f5c9e7736df92e5ced
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2450051Reviewed-by: Thomas Tellier <tellier@google.com>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813764}

chrome/browser/chromeos/login/session/user_session_manager.cc

@@ -2136,7 +2136,7 @@ EasyUnlockKeyManager* UserSessionManager::GetEasyUnlockKeyManager() {
 void UserSessionManager::DoBrowserLaunchInternal(Profile* profile,
                                                  LoginDisplayHost* login_host,
                                                  bool locale_pref_checked) {
-  if (browser_shutdown::IsTryingToQuit())
+  if (browser_shutdown::IsTryingToQuit() || chrome::IsAttemptingShutdown())
     return;
 
   if (!locale_pref_checked) {
@@ -2210,7 +2210,7 @@ void UserSessionManager::DoBrowserLaunchInternal(Profile* profile,
 void UserSessionManager::RespectLocalePreferenceWrapper(
     Profile* profile,
     const base::Closure& callback) {
-  if (browser_shutdown::IsTryingToQuit())
+  if (browser_shutdown::IsTryingToQuit() || chrome::IsAttemptingShutdown())
     return;
 
   const user_manager::User* const user =

chrome/browser/chromeos/login/wizard_controller.cc

@@ -1445,11 +1445,10 @@ void WizardController::OnOobeFlowFinished() {
 
   // Launch browser and delete login host controller.
   content::GetUIThreadTaskRunner({})->PostTask(
-      FROM_HERE,
-      base::BindOnce(&UserSessionManager::DoBrowserLaunch,
-                     base::Unretained(UserSessionManager::GetInstance()),
-                     ProfileManager::GetActiveUserProfile(),
-                     GetLoginDisplayHost()));
+      FROM_HERE, base::BindOnce(&UserSessionManager::DoBrowserLaunch,
+                                UserSessionManager::GetInstance()->AsWeakPtr(),
+                                ProfileManager::GetActiveUserProfile(),
+                                GetLoginDisplayHost()));
 }
 
 void WizardController::OnDeviceDisabledChecked(bool device_disabled) {