Remove balloon notification code. The last user was the Linux GTK port but that's deleted now.

chrome/browser/notifications/notification_prefs_manager.cc

-// Copyright (c) 2012 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 "chrome/browser/notifications/notification_prefs_manager.h"
-
-#include "base/prefs/pref_registry_simple.h"
-#include "base/prefs/pref_service.h"
-#include "chrome/common/pref_names.h"
-
-NotificationPrefsManager::NotificationPrefsManager(PrefService* prefs) {
-#if defined(OS_CHROMEOS)
-  static bool have_cleared = false;
-
-  if (!have_cleared) {
-    // Option menu for changing desktop notification position on ChromeOS is
-    // disabled. Force preference to default.
-    prefs->ClearPref(prefs::kDesktopNotificationPosition);
-    have_cleared = true;
-  }
-#endif
-}
-
-// static
-void NotificationPrefsManager::RegisterPrefs(PrefRegistrySimple* registry) {
-  registry->RegisterIntegerPref(prefs::kDesktopNotificationPosition,
-                                BalloonCollection::DEFAULT_POSITION);
-  registry->RegisterBooleanPref(prefs::kMessageCenterShowedFirstRunBalloon,
-                                false);
-}