Add a SigninAllowed policy.

chrome/browser/ui/browser_command_controller.cc

Index: chrome/browser/ui/browser_command_controller.cc
diff --git a/chrome/browser/ui/browser_command_controller.cc b/chrome/browser/ui/browser_command_controller.cc
index f4cd3bb7305be0a405e1543c08d8e8beb6a603b4..175b474281e1eabcc9b40d319367592b21ffa88e 100644
--- a/chrome/browser/ui/browser_command_controller.cc
+++ b/chrome/browser/ui/browser_command_controller.cc
@@ -16,6 +16,8 @@
 #include "chrome/browser/sessions/tab_restore_service.h"
 #include "chrome/browser/sessions/tab_restore_service_factory.h"
 #include "chrome/browser/shell_integration.h"
+#include "chrome/browser/signin/signin_manager.h"
+#include "chrome/browser/signin/signin_manager_factory.h"
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/browser/sync/profile_sync_service_factory.h"
 #include "chrome/browser/ui/bookmarks/bookmark_tab_helper.h"
@@ -202,6 +204,10 @@ BrowserCommandController::BrowserCommandController(
       prefs::kPrintingEnabled,
       base::Bind(&BrowserCommandController::UpdatePrintingState,
                  base::Unretained(this)));
+  pref_signin_allowed_.Init(prefs::kSigninAllowed,
+      profile()->GetOriginalProfile()->GetPrefs(),
+          base::Bind(&BrowserCommandController::OnSigninAllowedPrefChange,
+                     base::Unretained(this)));
 
   InitCommandState();
 
@@ -743,6 +749,17 @@ void BrowserCommandController::OnProfileAvatarChanged(
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// BrowserCommandController, SigninPrefObserver implementation:
+
+void BrowserCommandController::OnSigninAllowedPrefChange() {
+  // For unit tests, we don't have a window.
+  if (!window())
+    return;
+  const bool show_main_ui = IsShowingMainUI(window()->IsFullscreen());
+  command_updater_.UpdateCommandEnabled(IDC_SHOW_SYNC_SETUP,

[sail, 2013/02/08 20:18:57]

Move the code to update this state into a single function.

[Adrian Kuegel, 2013/02/11 16:47:30]

Done. Note that I had to pass show_main_ui as a parameter to the function, as
this value is determined differently at the three locations where the
IDC_SHOW_SYNC_SETUP command is updated. 

+      show_main_ui && pref_signin_allowed_.GetValue());
+}
+
 // BrowserCommandController, TabStripModelObserver implementation:
 
 void BrowserCommandController::TabInsertedAt(WebContents* contents,
@@ -883,7 +900,9 @@ void BrowserCommandController::InitCommandState() {
                                         !profile()->IsGuestSession() &&
                                         !profile()->IsOffTheRecord());
 
-  command_updater_.UpdateCommandEnabled(IDC_SHOW_SIGNIN, true);
+  command_updater_.UpdateCommandEnabled(
+      IDC_SHOW_SYNC_SETUP,
+      profile()->GetOriginalProfile()->IsSigninAllowed());
 
   // Initialize other commands based on the window type.
   bool normal_window = browser_->is_type_tabbed();
@@ -1118,6 +1137,8 @@ void BrowserCommandController::UpdateCommandsForFullscreenMode(
   // Show various bits of UI
   command_updater_.UpdateCommandEnabled(IDC_DEVELOPER_MENU, show_main_ui);
   command_updater_.UpdateCommandEnabled(IDC_FEEDBACK, show_main_ui);
+  command_updater_.UpdateCommandEnabled(IDC_SHOW_SYNC_SETUP,
+      show_main_ui && profile()->GetOriginalProfile()->IsSigninAllowed());
 
   // Settings page/subpages are forced to open in normal mode. We disable these
   // commands when incognito is forced.