WidgetDelegateView is its own contents view.

ash/shell/panel_window.h

 // 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.
 
 #ifndef ASH_SHELL_PANEL_WINDOW_H_
 #define ASH_SHELL_PANEL_WINDOW_H_
 
 #include "base/macros.h"
 #include "ui/aura/aura_export.h"
 #include "ui/views/widget/widget.h"
@@ skipping 20 matching lines @@
   // Creates a panel window and returns the associated widget.
   static views::Widget* CreatePanelWindow(const gfx::Rect& rect);
 
  private:
   // Overridden from views::View:
   gfx::Size GetPreferredSize() const override;
   void OnPaint(gfx::Canvas* canvas) override;
 
   // Overridden from views::WidgetDelegate:
   base::string16 GetWindowTitle() const override;
-  View* GetContentsView() override;
   bool CanResize() const override;
   bool CanMaximize() const override;
   bool CanMinimize() const override;
   views::NonClientFrameView* CreateNonClientFrameView(
       views::Widget* widget) override;
 
   std::string name_;
   views::Widget::InitParams params_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelWindow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_PANEL_WINDOW_H_