[ARC] Add browser test of ArcAuthService

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

Index: chrome/browser/chromeos/login/users/fake_chrome_user_manager.h
diff --git a/chrome/browser/chromeos/login/users/fake_chrome_user_manager.h b/chrome/browser/chromeos/login/users/fake_chrome_user_manager.h
index 8f5e7e3608f34d96e9a702ef6cf589157f73b62d..20084fb41e613a9ee6f6105c0dd5224432aba483 100644
--- a/chrome/browser/chromeos/login/users/fake_chrome_user_manager.h
+++ b/chrome/browser/chromeos/login/users/fake_chrome_user_manager.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "chrome/browser/chromeos/login/user_flow.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
+#include "components/prefs/testing_pref_service.h"
 #include "components/user_manager/fake_user_manager.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_image/user_image.h"
@@ -44,6 +45,10 @@ class FakeChromeUserManager : public ChromeUserManager {
   const user_manager::User* AddUserWithAffiliation(const AccountId& account_id,
                                                    bool is_affiliated);
 
+  // Creates the instance returned by |GetLocalState()| (which returns nullptr
+  // by default).
+  void CreateLocalState();
+
   // user_manager::UserManager override.
   void Shutdown() override;
   const user_manager::UserList& GetUsers() const override;
@@ -206,6 +211,8 @@ class FakeChromeUserManager : public ChromeUserManager {
 
   using FlowMap = std::map<AccountId, UserFlow*>;
 
+  std::unique_ptr<TestingPrefServiceSimple> local_state_;
+
   // Specific flows by user e-mail.
   // Keys should be canonicalized before access.
   FlowMap specific_flows_;