Add a SigninAllowed policy.

chrome/browser/ui/webui/ntp/new_tab_page_sync_handler.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_NTP_NEW_TAB_PAGE_SYNC_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_NEW_TAB_PAGE_SYNC_HANDLER_H_
 
 #include <string>
 
+#include "chrome/browser/signin/signin_pref_observer.h"
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/browser/sync/sync_ui_util.h"
 #include "content/public/browser/web_ui_message_handler.h"
 
+class SigninPrefObserver;
+
 namespace base {
 class ListValue;
 }
 
 // Sends sync-state changes to the New Tab Page for UI updating and forwards
 // link clicks on the page to the sync service.
 class NewTabPageSyncHandler : public content::WebUIMessageHandler,
-                              public ProfileSyncServiceObserver {
+                              public ProfileSyncServiceObserver,
+                              public SigninPrefObserver {
  public:
   NewTabPageSyncHandler();
   virtual ~NewTabPageSyncHandler();
 
   // WebUIMessageHandler implementation.
   virtual void RegisterMessages() OVERRIDE;
 
   // Callback for "GetSyncMessage".
   void HandleGetSyncMessage(const base::ListValue* args);
   // Callback for "SyncLinkClicked".
   void HandleSyncLinkClicked(const base::ListValue* args);
 
   // ProfileSyncServiceObserver
   virtual void OnStateChanged() OVERRIDE;
 
+  // SigninPrefObserver
+  virtual void OnSigninAllowedPrefChange(bool signin_allowed) OVERRIDE;
+
  private:
   enum MessageType {
     HIDE,
     SYNC_ERROR,
     SYNC_PROMO
   };
   // Helper to invoke the |syncMessageChanged| JS function on the new tab page.
   void SendSyncMessageToPage(MessageType type,
                              std::string msg, std::string linktext);
 
@@ skipping 13 matching lines @@
   ProfileSyncService* sync_service_;
 
   // Used to make sure we don't register ourselves twice if the user refreshes
   // the new tab page.
   bool waiting_for_initial_page_load_;
 
   DISALLOW_COPY_AND_ASSIGN(NewTabPageSyncHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NTP_NEW_TAB_PAGE_SYNC_HANDLER_H_