Migrate call sites LoginDisplayHostImpl::default_host to LoginDisplayHost.

chrome/browser/chromeos/login/test/oobe_screen_waiter.cc

 // Copyright 2013 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/test/oobe_screen_waiter.h"
 
-#include "chrome/browser/chromeos/login/ui/login_display_host_impl.h"
+#include "chrome/browser/chromeos/login/ui/login_display_host.h"
 #include "content/public/test/test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace chromeos {
 
 OobeScreenWaiter::OobeScreenWaiter(OobeDisplay::Screen expected_screen)
     : waiting_for_screen_(false),
       expected_screen_(expected_screen) {
 }
 
@@ skipping 25 matching lines @@
     OobeDisplay::Screen current_screen,
     OobeDisplay::Screen new_screen) {
   if (waiting_for_screen_ && new_screen == expected_screen_) {
     runner_->Quit();
     waiting_for_screen_ = false;
     GetOobeUI()->RemoveObserver(this);
   }
 }
 
 OobeUI* OobeScreenWaiter::GetOobeUI() {
-  OobeUI* oobe_ui = static_cast<chromeos::LoginDisplayHostImpl*>(
-      chromeos::LoginDisplayHostImpl::default_host())->GetOobeUI();
+  OobeUI* oobe_ui = LoginDisplayHost::default_host()->GetOobeUI();
   CHECK(oobe_ui);
   return oobe_ui;
 }
 
 }  // namespace chromeos