WidgetDelegateView is its own contents view.

ash/shell/lock_view.cc

 // 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.
 
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm_shell.h"
 #include "ash/shell.h"
 #include "ash/shell/example_factory.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 74 matching lines @@
   gfx::Size ps = lock_view->GetPreferredSize();
 
   gfx::Size root_window_size = Shell::GetPrimaryRootWindow()->bounds().size();
   params.bounds = gfx::Rect((root_window_size.width() - ps.width()) / 2,
                             (root_window_size.height() - ps.height()) / 2,
                             ps.width(), ps.height());
   params.delegate = lock_view;
   params.parent = Shell::GetContainer(Shell::GetPrimaryRootWindow(),
                                       kShellWindowId_LockScreenContainer);
   widget->Init(params);
-  widget->SetContentsView(lock_view);
   widget->Show();
   widget->GetNativeView()->SetName("LockView");
   widget->GetNativeView()->Focus();
 
   // TODO: it shouldn't be necessary to invoke UpdateTooltip() here.
   Shell::GetInstance()->tooltip_controller()->UpdateTooltip(
       widget->GetNativeView());
 }
 
 }  // namespace shell
 }  // namespace ash