Do not create login items if the user deleted a previous one.

chrome/browser/background/background_mode_manager_mac.mm

 // 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.
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/mac/mac_util.h"
 #include "chrome/browser/background/background_mode_manager.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
 using content::BrowserThread;
 
 namespace {
+#if !defined(NDEBUG)
+// The code to remove a login item has a potential race (because the code to
+// set and check the kUserRemovedLoginItem pref runs on the UI thread, while
+// the code that checks for a login item runs on the IO thread). We add this
+// flag which should always match the value of the pref to see if we ever hit
+// this race in practice.
+static bool login_item_removed = false;
+#endif
+
+void SetUserRemovedLoginItemPrefCallback() {
+  PrefService* service = g_browser_process->local_state();
+  service->SetBoolean(prefs::kUserRemovedLoginItem, true);
+}
 
 void DisableLaunchOnStartupCallback() {
   // Check if Chrome is not a login Item, or is a Login Item but w/o 'hidden'
   // flag - most likely user has modified the setting, don't override it.
   bool is_hidden = false;
-  if (!base::mac::CheckLoginItemStatus(&is_hidden) || !is_hidden)
+  if (!base::mac::CheckLoginItemStatus(&is_hidden)) {
+    // No login item - this means the user must have already removed it, so
+    // call back to the UI thread to set a preference so we don't try to
+    // recreate it the next time they enable/install a background app.
+#if !defined(NDEBUG)
+    login_item_removed = true;
+#endif
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                            base::Bind(SetUserRemovedLoginItemPrefCallback));
+    return;
+  }
+
+  // If the login item does not have the "hidden" flag set, just leave it there
+  // since it means the user must have created it.
+  if (!is_hidden)
     return;
 
+  // Remove the login item we created.
   base::mac::RemoveFromLoginItems();
 }
 
 void SetUserCreatedLoginItemPrefCallback() {
   PrefService* service = g_browser_process->local_state();
   service->SetBoolean(prefs::kUserCreatedLoginItem, true);
 }
 
-void EnableLaunchOnStartupCallback() {
-  // Return if Chrome is already a Login Item (avoid overriding user choice).
+void EnableLaunchOnStartupCallback(bool should_add_login_item) {
+  // Check if Chrome is already a Login Item (avoid overriding user choice).
   if (base::mac::CheckLoginItemStatus(NULL)) {
     // Call back to the UI thread to set our preference so we don't delete the
     // user's login item when we disable launch on startup. There's a race
     // condition here if the user disables launch on startup before our callback
     // is run, but the user can manually disable "Open At Login" via the dock if
     // this happens.
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                             base::Bind(SetUserCreatedLoginItemPrefCallback));
     return;
   }
 
-  base::mac::AddToLoginItems(true);  // Hide on startup.
+  if (should_add_login_item)
+    base::mac::AddToLoginItems(true);  // Hide on startup.
+#if !defined(NDEBUG)
+  else
+    DCHECK(!login_item_removed); // Check for race condition (see above).
+#endif
 }
 
 }  // namespace
 
 void BackgroundModeManager::EnableLaunchOnStartup(bool should_launch) {
   // This functionality is only defined for default profile, currently.
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kUserDataDir))
     return;
 
   if (should_launch) {
+    PrefService* service = g_browser_process->local_state();
+    // Create a login item if the user did not remove our login item
+    // previously. We call out to the FILE thread either way since we
+    // want to check for a user-created login item.
+    bool should_add_login_item =
+        !service->GetBoolean(prefs::kUserRemovedLoginItem);
     BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
-                            base::Bind(EnableLaunchOnStartupCallback));
+                            base::Bind(EnableLaunchOnStartupCallback,
+                                       should_add_login_item));
   } else {
     PrefService* service = g_browser_process->local_state();
     if (service->GetBoolean(prefs::kUserCreatedLoginItem)) {
-      // We didn't create the login item, so nothing to do here.
+      // We didn't create the login item, so nothing to do here. Clear our
+      // prefs so if the user removes the login item before installing a
+      // background app, we will revert to the default behavior.
       service->ClearPref(prefs::kUserCreatedLoginItem);
+      service->ClearPref(prefs::kUserRemovedLoginItem);
+#if !defined(NDEBUG)
+      login_item_removed = false;
+#endif
       return;
     }
     // Call to the File thread to remove the login item since it requires
     // accessing the disk.
     BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
                             base::Bind(DisableLaunchOnStartupCallback));
   }
 }
 
 void BackgroundModeManager::DisplayAppInstalledNotification(
     const extensions::Extension* extension) {
   // TODO(atwilson): Display a platform-appropriate notification here.
   // http://crbug.com/74970
 }
 
 string16 BackgroundModeManager::GetPreferencesMenuLabel() {
   return l10n_util::GetStringUTF16(IDS_OPTIONS);
 }