Remove enable Drive offline system tray UI.

ash/system/tray/system_tray_notifier.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 "ash/system/tray/system_tray_notifier.h"
 
 #if defined(OS_CHROMEOS)
 #include "ash/system/chromeos/network/network_state_notifier.h"
 #endif
 
@@ skipping 202 matching lines @@
                     OnSystemClockTimeUpdated());
 }
 
 void SystemTrayNotifier::NotifyDriveJobUpdated(
     const DriveOperationStatus& status) {
   FOR_EACH_OBSERVER(DriveObserver,
                     drive_observers_,
                     OnDriveJobUpdated(status));
 }
 
-void SystemTrayNotifier::NotifyDriveOfflineEnabled() {
-  FOR_EACH_OBSERVER(DriveObserver,
-                    drive_observers_,
-                    OnDriveOfflineEnabled());
-}
-
 void SystemTrayNotifier::NotifyRefreshIME(bool show_message) {
   FOR_EACH_OBSERVER(IMEObserver,
                     ime_observers_,
                     OnIMERefresh(show_message));
 }
 
 void SystemTrayNotifier::NotifyShowLoginButtonChanged(bool show_login_button) {
   FOR_EACH_OBSERVER(LogoutButtonObserver,
                     logout_button_observers_,
                     OnShowLogoutButtonInTrayChanged(show_login_button));
@@ skipping 74 matching lines @@
 }
 
 void SystemTrayNotifier::NotifyScreenShareStop() {
   FOR_EACH_OBSERVER(ScreenShareObserver, screen_share_observers_,
                     OnScreenShareStop());
 }
 
 #endif  // OS_CHROMEOS
 
 }  // namespace ash