Make the user manager UI not permit guest mode when preferences dictate

chrome/browser/ui/webui/signin/user_manager_screen_handler.cc

Index: chrome/browser/ui/webui/signin/user_manager_screen_handler.cc
diff --git a/chrome/browser/ui/webui/signin/user_manager_screen_handler.cc b/chrome/browser/ui/webui/signin/user_manager_screen_handler.cc
index b88e63136a0c2c9c5c8f3eb62858d830116a76e3..87c8c69c79af33d8a724dabcedfa9d205b09aee8 100644
--- a/chrome/browser/ui/webui/signin/user_manager_screen_handler.cc
+++ b/chrome/browser/ui/webui/signin/user_manager_screen_handler.cc
@@ -11,6 +11,7 @@
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/api/screenlock_private/screenlock_private_api.h"
+#include "chrome/browser/prefs/incognito_mode_prefs.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_avatar_icon_util.h"
 #include "chrome/browser/profiles/profile_info_cache.h"
@@ -144,6 +145,15 @@ extensions::ScreenlockPrivateEventRouter* GetScreenlockRouter(
       profile);
 }
 
+bool IsGuestModeEnabled() {
+  PrefService* service = g_browser_process->local_state();
+  DCHECK(service);
+  if (IncognitoModePrefs::GetAvailability(service) ==
+      IncognitoModePrefs::DISABLED)
+    return false;

[Nikita (slow), 2014/08/14 15:53:07]

nit: Add {}

+  return service->GetBoolean(prefs::kBrowserGuestModeEnabled);
+}
+
 }  // namespace
 
 // ProfileUpdateObserver ------------------------------------------------------
@@ -284,7 +294,8 @@ void UserManagerScreenHandler::Unlock(const std::string& user_email) {
 
 void UserManagerScreenHandler::HandleInitialize(const base::ListValue* args) {
   SendUserList();
-  web_ui()->CallJavascriptFunction("cr.ui.Oobe.showUserManagerScreen");
+  web_ui()->CallJavascriptFunction("cr.ui.Oobe.showUserManagerScreen",
+      base::FundamentalValue(IsGuestModeEnabled()));
   desktop_type_ = chrome::GetHostDesktopTypeForNativeView(
       web_ui()->GetWebContents()->GetNativeView());
 
@@ -372,9 +383,15 @@ void UserManagerScreenHandler::HandleRemoveUser(const base::ListValue* args) {
 }
 
 void UserManagerScreenHandler::HandleLaunchGuest(const base::ListValue* args) {
-  profiles::SwitchToGuestProfile(desktop_type_,
-                                 base::Bind(&OnSwitchToProfileComplete));
-  ProfileMetrics::LogProfileSwitchUser(ProfileMetrics::SWITCH_PROFILE_GUEST);
+  if (IsGuestModeEnabled()) {
+    profiles::SwitchToGuestProfile(desktop_type_,
+                                   base::Bind(&OnSwitchToProfileComplete));
+    ProfileMetrics::LogProfileSwitchUser(ProfileMetrics::SWITCH_PROFILE_GUEST);
+  } else {
+    // The UI should have prevented the user from allowing the selection of
+    // guest mode.
+    NOTREACHED();
+  }
 }
 
 void UserManagerScreenHandler::HandleLaunchUser(const base::ListValue* args) {
@@ -628,7 +645,7 @@ void UserManagerScreenHandler::SendUserList() {
   }
 
   web_ui()->CallJavascriptFunction("login.AccountPickerScreen.loadUsers",
-    users_list, base::FundamentalValue(true));
+      users_list, base::FundamentalValue(IsGuestModeEnabled()));
 }
 
 void UserManagerScreenHandler::ReportAuthenticationResult(