Revert of Fold UpdateModel into UpdateScreen.

chrome/browser/chromeos/login/screens/mock_update_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/mock_update_screen.h"
 
 using ::testing::AtLeast;
 using ::testing::_;
 
 namespace chromeos {
 
 MockUpdateScreen::MockUpdateScreen(BaseScreenDelegate* base_screen_delegate,
                                    UpdateView* view)
     : UpdateScreen(base_screen_delegate, view, NULL) {
 }
 
 MockUpdateScreen::~MockUpdateScreen() {
 }
 
-MockUpdateView::MockUpdateView() {
+MockUpdateView::MockUpdateView() : model_(nullptr) {
   EXPECT_CALL(*this, MockBind(_)).Times(AtLeast(1));
 }
 
 MockUpdateView::~MockUpdateView() {
-  if (screen_)
-    screen_->OnViewDestroyed(this);
+  if (model_)
+    model_->OnViewDestroyed(this);
 }
 
-void MockUpdateView::Bind(UpdateScreen* screen) {
-  screen_ = screen;
-  MockBind(screen);
+void MockUpdateView::Bind(UpdateModel& model) {
+  model_ = &model;
+  MockBind(model);
 }
 
 void MockUpdateView::Unbind() {
-  screen_ = nullptr;
+  model_ = nullptr;
   MockUnbind();
 }
 
 }  // namespace chromeos