cros: Remove unused method

chrome/browser/chromeos/login/screens/device_disabled_screen.cc

 // Copyright 2014 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/chromeos/login/screens/device_disabled_screen.h"
 
 #include <string>
 
 #include "base/logging.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 15 matching lines @@
     actor_->SetDelegate(this);
   device_disabling_manager_->AddObserver(this);
 }
 
 DeviceDisabledScreen::~DeviceDisabledScreen() {
   if (actor_)
     actor_->SetDelegate(nullptr);
   device_disabling_manager_->RemoveObserver(this);
 }
 
-void DeviceDisabledScreen::PrepareToShow() {
-}
-
 void DeviceDisabledScreen::Show() {
   if (!actor_ || showing_)
     return;
 
   showing_ = true;
   actor_->Show();
 }
 
 void DeviceDisabledScreen::Hide() {
   if (!showing_)
@@ skipping 21 matching lines @@
   return device_disabling_manager_->disabled_message();
 }
 
 void DeviceDisabledScreen::OnDisabledMessageChanged(
     const std::string& disabled_message) {
   if (actor_)
     actor_->UpdateMessage(disabled_message);
 }
 
 }  // namespace chromeos