Disabled ARC for ephemeral users.

chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc

 // Copyright 2015 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/users/fake_chrome_user_manager.h"
 
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "base/sys_info.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
@@ skipping 121 matching lines @@
     delete it->second;
     specific_flows_.erase(it);
   }
 }
 
 void FakeChromeUserManager::SwitchActiveUser(const AccountId& account_id) {
   active_account_id_ = account_id;
   ProfileHelper::Get()->ActiveUserHashChanged(
       ProfileHelper::GetUserIdHashByUserIdForTesting(
           account_id.GetUserEmail()));
+  active_user_ = nullptr;
   if (!users_.empty() && active_account_id_.is_valid()) {
-    for (user_manager::User* user : users_)
-      user->set_is_active(user->GetAccountId() == active_account_id_);
+    for (user_manager::User* const user : users_) {
+      if (user->GetAccountId() == active_account_id_) {
+        active_user_ = user;
+        user->set_is_active(true);
+      } else {
+        user->set_is_active(false);
+      }
+    }
   }
 }
 
 const AccountId& FakeChromeUserManager::GetOwnerAccountId() const {
   return owner_account_id_;
 }
 
 void FakeChromeUserManager::SessionStarted() {
 }
 
@@ skipping 114 matching lines @@
   NOTIMPLEMENTED();
   return;
 }
 
 bool FakeChromeUserManager::IsValidDefaultUserImageId(int image_index) const {
   NOTIMPLEMENTED();
   return false;
 }
 
 }  // namespace chromeos