Add a SigninAllowed policy.

chrome/browser/ui/webui/ntp/new_tab_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 "build/build_config.h"
 
 #include "chrome/browser/ui/webui/ntp/new_tab_ui.h"
 
 #include <set>
 
@@ skipping 98 matching lines @@
   if (!GetProfile()->IsOffTheRecord()) {
     web_ui->AddMessageHandler(new browser_sync::ForeignSessionHandler());
     web_ui->AddMessageHandler(new MostVisitedHandler());
     web_ui->AddMessageHandler(new RecentlyClosedTabsHandler());
     web_ui->AddMessageHandler(new MetricsHandler());
 #if !defined(OS_ANDROID)
     web_ui->AddMessageHandler(new NewTabPageHandler());
     if (NewTabUI::IsDiscoveryInNTPEnabled())
       web_ui->AddMessageHandler(new SuggestionsHandler());
     // Android doesn't have a sync promo/username on NTP.
-    web_ui->AddMessageHandler(new NewTabPageSyncHandler());
+    if (GetProfile()->IsSigninAllowed())
+      web_ui->AddMessageHandler(new NewTabPageSyncHandler());
 
     // Or apps.
     if (ShouldShowApps()) {
       ExtensionService* service = GetProfile()->GetExtensionService();
       // We might not have an ExtensionService (on ChromeOS when not logged in
       // for example).
       if (service)
         web_ui->AddMessageHandler(new AppLauncherHandler(service));
     }
 #endif
@@ skipping 297 matching lines @@
 void NewTabUI::NewTabHTMLSource::AddResource(const char* resource,
                                              const char* mime_type,
                                              int resource_id) {
   DCHECK(resource);
   DCHECK(mime_type);
   resource_map_[std::string(resource)] =
       std::make_pair(std::string(mime_type), resource_id);
 }
 
 NewTabUI::NewTabHTMLSource::~NewTabHTMLSource() {}