cros: Remove unused method.

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

 // 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 "chrome/browser/chromeos/login/screens/base_screen.h"
 
 #include "base/logging.h"
 #include "chrome/browser/chromeos/login/screens/base_screen_delegate.h"
 #include "chrome/browser/chromeos/login/screens/model_view_channel.h"
 
@@ skipping 74 matching lines @@
 void BaseScreen::OnHide() {
 }
 
 void BaseScreen::OnClose() {
 }
 
 bool BaseScreen::IsStatusAreaDisplayed() {
   return true;
 }
 
-bool BaseScreen::IsPermanent() {
-  return false;
-}
-
 std::string BaseScreen::GetID() const {
   // TODO (ygorshenin, crbug.com/433797): elimitate intermediate
   // GetName() ASAP.
   return GetName();
 }
 
 void BaseScreen::CommitContextChanges() {
   if (!context_.HasChanges())
     return;
   if (!channel_) {
@@ skipping 29 matching lines @@
 }
 
 void BaseScreen::OnContextChanged(const base::DictionaryValue& diff) {
   std::vector<::login::ScreenContext::KeyType> keys;
   context_.ApplyChanges(diff, &keys);
   for (const auto& key : keys)
     OnContextKeyUpdated(key);
 }
 
 }  // namespace chromeos