Revert of Delete dead signin code (SigninGlobalError)

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 c007a8ea1eea53b2aaa778ae62d426cb93c9f783..abb123388f0c36b7d5397e6fb790a9d34ad81506 100644
--- a/chrome/browser/ui/browser_command_controller.cc
+++ b/chrome/browser/ui/browser_command_controller.cc
@@ -229,6 +229,11 @@
       base::Bind(&BrowserCommandController::UpdateCommandsForFullscreenMode,
                  base::Unretained(this)));
 #endif
+  pref_signin_allowed_.Init(
+      prefs::kSigninAllowed,
+      profile()->GetOriginalProfile()->GetPrefs(),
+      base::Bind(&BrowserCommandController::OnSigninAllowedPrefChange,
+                 base::Unretained(this)));
 
   InitCommandState();
 
@@ -759,6 +764,9 @@
     case IDC_HELP_PAGE_VIA_MENU:
       ShowHelp(browser_, HELP_SOURCE_MENU);
       break;
+    case IDC_SHOW_SIGNIN:
+      ShowBrowserSigninOrSettings(browser_, signin_metrics::SOURCE_MENU);
+      break;
     case IDC_TOGGLE_SPEECH_INPUT:
       ToggleSpeechInput(browser_);
       break;
@@ -775,6 +783,16 @@
       LOG(WARNING) << "Received Unimplemented Command: " << id;
       break;
   }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// BrowserCommandController, SigninPrefObserver implementation:
+
+void BrowserCommandController::OnSigninAllowedPrefChange() {
+  // For unit tests, we don't have a window.
+  if (!window())
+    return;
+  UpdateShowSyncState(IsShowingMainUI());
 }
 
 // BrowserCommandController, TabStripModelObserver implementation:
@@ -966,6 +984,8 @@
   }
 #endif
 
+  UpdateShowSyncState(true);
+
   // Navigation commands
   command_updater_.UpdateCommandEnabled(
       IDC_HOME,
@@ -1050,6 +1070,7 @@
   command_updater->UpdateCommandEnabled(IDC_IMPORT_SETTINGS, !forced_incognito);
   command_updater->UpdateCommandEnabled(IDC_OPTIONS,
                                         !forced_incognito || guest_session);
+  command_updater->UpdateCommandEnabled(IDC_SHOW_SIGNIN, !forced_incognito);
 }
 
 void BrowserCommandController::UpdateCommandsForIncognitoAvailability() {
@@ -1228,6 +1249,7 @@
 #if defined(GOOGLE_CHROME_BUILD)
   command_updater_.UpdateCommandEnabled(IDC_FEEDBACK, show_main_ui);
 #endif
+  UpdateShowSyncState(show_main_ui);
 
   // Settings page/subpages are forced to open in normal mode. We disable these
   // commands for guest sessions and when incognito is forced.
@@ -1277,6 +1299,11 @@
   command_updater_.UpdateCommandEnabled(IDC_SAVE_PAGE, CanSavePage(browser_));
 }
 
+void BrowserCommandController::UpdateShowSyncState(bool show_main_ui) {
+  command_updater_.UpdateCommandEnabled(
+      IDC_SHOW_SYNC_SETUP, show_main_ui && pref_signin_allowed_.GetValue());
+}
+
 // static
 void BrowserCommandController::UpdateOpenFileState(
     CommandUpdater* command_updater) {