Add new BrowserForceSigninEnabeld policy option with future:true flag.

chrome/browser/profiles/profiles_state.cc

 // Copyright 2013 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/profiles/profiles_state.h"
 
 #include <stddef.h>
 
 #include "base/files/file_path.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 41 matching lines @@
 
 void RegisterPrefs(PrefRegistrySimple* registry) {
   // Preferences about global profile information.
   registry->RegisterStringPref(prefs::kProfileLastUsed, std::string());
   registry->RegisterIntegerPref(prefs::kProfilesNumCreated, 1);
   registry->RegisterListPref(prefs::kProfilesLastActive);
 
   // Preferences about the user manager.
   registry->RegisterBooleanPref(prefs::kBrowserGuestModeEnabled, true);
   registry->RegisterBooleanPref(prefs::kBrowserAddPersonEnabled, true);
+  registry->RegisterBooleanPref(prefs::kForceBrowserSignin, false);
 
   registry->RegisterBooleanPref(
       prefs::kProfileAvatarRightClickTutorialDismissed, false);
 }
 
 base::string16 GetAvatarNameForProfile(const base::FilePath& profile_path) {
   base::string16 display_name;
 
   if (profile_path == ProfileManager::GetGuestProfilePath()) {
     display_name = l10n_util::GetStringUTF16(IDS_GUEST_PROFILE_NAME);
@@ skipping 199 matching lines @@
       at_least_one_regular_profile_present = true;
 
       if (!entry->IsSigninRequired())
         return false;
     }
   }
   return at_least_one_regular_profile_present;
 }
 
 }  // namespace profiles