Remove enable Drive offline system tray UI.

ash/system/tray/system_tray_notifier.h

 // 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.
 
 #ifndef ASH_SYSTEM_TRAY_SYSTEM_TRAY_NOTIFIER_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_NOTIFIER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 83 matching lines @@
   void NotifyAccessibilityModeChanged(
       AccessibilityNotificationVisibility notify);
   void NotifyTracingModeChanged(bool value);
   void NotifyRefreshBluetooth();
   void NotifyBluetoothDiscoveringChanged();
   void NotifyCapsLockChanged(bool enabled, bool search_mapped_to_caps_lock);
   void NotifyRefreshClock();
   void NotifyDateFormatChanged();
   void NotifySystemClockTimeUpdated();
   void NotifyDriveJobUpdated(const DriveOperationStatus& status);
-  void NotifyDriveOfflineEnabled();
   void NotifyRefreshIME(bool show_message);
   void NotifyShowLoginButtonChanged(bool show_login_button);
   void NotifyLocaleChanged(LocaleObserver::Delegate* delegate,
                            const std::string& cur_locale,
                            const std::string& from_locale,
                            const std::string& to_locale);
   void NotifySessionStartTimeChanged();
   void NotifySessionLengthLimitChanged();
   void NotifyUpdateRecommended(UpdateObserver::UpdateSeverity severity);
   void NotifyUserUpdate();
@@ skipping 33 matching lines @@
   ObserverList<ScreenShareObserver> screen_share_observers_;
   scoped_ptr<NetworkStateNotifier> network_state_notifier_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayNotifier);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_NOTIFIER_H_