Add a SigninAllowed policy.

chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc

 // Copyright (c) 2012 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/ui/webui/sync_promo/sync_promo_ui.h"
 
 #include "base/command_line.h"
 #include "base/prefs/pref_service.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
@@ skipping 114 matching lines @@
   return false;
 #else
 
   // Don't bother if we don't have any kind of network connection.
   if (net::NetworkChangeNotifier::IsOffline())
     return false;
 
   // Display the signin promo if the user is not signed in.
   SigninManager* signin = SigninManagerFactory::GetForProfile(
       profile->GetOriginalProfile());
-  return signin->GetAuthenticatedUsername().empty();
+  return signin->IsSigninAllowed() &&
+      signin->GetAuthenticatedUsername().empty();
 #endif
 }
 
 // static
 void SyncPromoUI::RegisterUserPrefs(PrefRegistrySyncable* registry) {
   registry->RegisterIntegerPref(prefs::kSyncPromoStartupCount, 0,
                                 PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterBooleanPref(prefs::kSyncPromoUserSkipped, false,
                                 PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterBooleanPref(prefs::kSyncPromoShowOnFirstRunAllowed, true,
@@ skipping 155 matching lines @@
       g_force_web_based_signin_flow;
 #else
   return false;
 #endif
 }
 
 // static
 void SyncPromoUI::ForceWebBasedSigninFlowForTesting(bool force) {
   g_force_web_based_signin_flow = force;
 }