Restore last used user session after crash

components/user_manager/user_manager_base.cc

Index: components/user_manager/user_manager_base.cc
diff --git a/components/user_manager/user_manager_base.cc b/components/user_manager/user_manager_base.cc
index 8ca4df541903af968a2b0651bf8fcd632214bbd8..adc07078efc6d8b5adc35fa67a3b08228799252f 100644
--- a/components/user_manager/user_manager_base.cc
+++ b/components/user_manager/user_manager_base.cc
@@ -62,6 +62,11 @@ const char kUserForceOnlineSignin[] = "UserForceOnlineSignin";
 // kiosk, public account, etc.).
 const char kLastLoggedInRegularUser[] = "LastLoggedInRegularUser";
 
+// A string pref containing the ID of the last active user.
+// In case of browser crash, this pref will be used to set active user after
+// session restore.
+const char kLastActiveUser[] = "LastActiveUser";
+
 // Upper bound for a histogram metric reporting the amount of time between
 // one regular user logging out and a different regular user logging in.
 const int kLogoutToLoginDelayMaxSec = 1800;
@@ -94,6 +99,7 @@ void UserManagerBase::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterDictionaryPref(kUserDisplayEmail);
   registry->RegisterDictionaryPref(kUserOAuthTokenStatus);
   registry->RegisterDictionaryPref(kUserForceOnlineSignin);
+  registry->RegisterStringPref(kLastActiveUser, std::string());
 }
 
 UserManagerBase::UserManagerBase(
@@ -108,6 +114,7 @@ UserManagerBase::UserManagerBase(
       is_current_user_ephemeral_regular_user_(false),
       ephemeral_users_enabled_(false),
       manager_creation_time_(base::TimeTicks::Now()),
+      last_session_active_user_initialized_(false),
       task_runner_(task_runner),
       blocking_task_runner_(blocking_task_runner),
       weak_factory_(this) {
@@ -153,6 +160,11 @@ void UserManagerBase::UserLoggedIn(const std::string& user_id,
                                    bool browser_restart) {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
 
+  if (!last_session_active_user_initialized_) {
+    last_session_active_user_ = GetLocalState()->GetString(kLastActiveUser);
+    last_session_active_user_initialized_ = true;
+  }
+
   User* user = FindUserInListAndModify(user_id);
   if (active_user_ && user) {
     user->set_is_logged_in(true);
@@ -256,6 +268,17 @@ void UserManagerBase::SwitchActiveUser(const std::string& user_id) {
   NotifyActiveUserChanged(active_user_);
 }
 
+void UserManagerBase::SwitchToLastActiveUser() {
+  if (last_session_active_user_.empty())
+    return;
+
+  if (GetActiveUser()->email() != last_session_active_user_)
+    SwitchActiveUser(last_session_active_user_);
+
+  // Make sure that this function gets run only once.
+  last_session_active_user_.clear();
+}
+
 void UserManagerBase::SessionStarted() {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
   session_started_ = true;
@@ -882,6 +905,10 @@ void UserManagerBase::RemoveNonCryptohomeData(const std::string& user_id) {
 
   DictionaryPrefUpdate prefs_force_online_update(prefs, kUserForceOnlineSignin);
   prefs_force_online_update->RemoveWithoutPathExpansion(user_id, NULL);
+
+  std::string last_active_user = GetLocalState()->GetString(kLastActiveUser);
+  if (user_id == last_active_user)
+    GetLocalState()->SetString(kLastActiveUser, std::string());
 }
 
 User* UserManagerBase::RemoveRegularOrSupervisedUserFromList(
@@ -963,6 +990,9 @@ void UserManagerBase::UpdateLoginState() {
 }
 
 void UserManagerBase::SetLRUUser(User* user) {
+  GetLocalState()->SetString(kLastActiveUser, user->email());
+  GetLocalState()->CommitPendingWrite();
+
   UserList::iterator it =
       std::find(lru_logged_in_users_.begin(), lru_logged_in_users_.end(), user);
   if (it != lru_logged_in_users_.end())