Add new BrowserForceSigninEnabeld policy option with future:true flag.

chrome/browser/policy/configuration_policy_handler_list_factory.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/policy/configuration_policy_handler_list_factory.h"
 
 #include <limits.h>
 #include <stddef.h>
 
 #include <utility>
@@ skipping 555 matching lines @@
 #if !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
   { key::kNativeMessagingUserLevelHosts,
     extensions::pref_names::kNativeMessagingUserLevelHosts,
     base::Value::TYPE_BOOLEAN },
   { key::kBrowserGuestModeEnabled,
     prefs::kBrowserGuestModeEnabled,
     base::Value::TYPE_BOOLEAN },
   { key::kBrowserAddPersonEnabled,
     prefs::kBrowserAddPersonEnabled,
     base::Value::TYPE_BOOLEAN },
+  { key::kForceBrowserSignin,
+    prefs::kForceBrowserSignin,
+    base::Value::TYPE_BOOLEAN },
 #endif  // !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
 
 #if defined(OS_WIN)
   { key::kWelcomePageOnOSUpgradeEnabled,
     prefs::kWelcomePageOnOSUpgradeEnabled,
     base::Value::TYPE_BOOLEAN },
 #endif  // OS_WIN
 
 #if !defined(OS_ANDROID)
   { key::kSuppressUnsupportedOSWarning,
@@ skipping 292 matching lines @@
       SimpleSchemaValidatingPolicyHandler::MANDATORY_PROHIBITED)));
   handlers->AddHandler(
       base::MakeUnique<chromeos::KeyPermissionsPolicyHandler>(chrome_schema));
   handlers->AddHandler(base::WrapUnique(new DefaultGeolocationPolicyHandler()));
 #endif  // defined(OS_CHROMEOS)
 
   return handlers;
 }
 
 }  // namespace policy