Add a SigninAllowed policy.

chrome/browser/ui/webui/options/browser_options_handler.h

Index: chrome/browser/ui/webui/options/browser_options_handler.h
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.h b/chrome/browser/ui/webui/options/browser_options_handler.h
index 3824c99541016161fa9925705324bc68c1042641..93ebf490759090149729fb0fda358044f87b2cab 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.h
+++ b/chrome/browser/ui/webui/options/browser_options_handler.h
@@ -14,6 +14,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search_engines/template_url_service_observer.h"
 #include "chrome/browser/shell_integration.h"
+#include "chrome/browser/signin/signin_pref_observer.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "ui/base/models/table_model_observer.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
@@ -36,6 +37,7 @@ class BrowserOptionsHandler
     : public OptionsPageUIHandler,
       public CloudPrintSetupHandlerDelegate,
       public ProfileSyncServiceObserver,
+      public SigninPrefObserver,
       public ui::SelectFileDialog::Listener,
       public ShellIntegration::DefaultWebClientObserver,
 #if defined(OS_CHROMEOS)
@@ -56,6 +58,9 @@ class BrowserOptionsHandler
   // ProfileSyncServiceObserver implementation.
   virtual void OnStateChanged() OVERRIDE;
 
+  // SigninPrefObserver implementation.
+  virtual void OnSigninAllowedPrefChange(bool signin_allowed) OVERRIDE;
+
   // ShellIntegration::DefaultWebClientObserver implementation.
   virtual void SetDefaultWebClientUIState(
       ShellIntegration::DefaultWebClientUIState state) OVERRIDE;