WidgetDelegateView is its own contents view.

ui/message_center/views/toast_contents_view.h

 // Copyright (c) 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.
 
 #ifndef UI_MESSAGE_CENTER_VIEWS_TOAST_CONTENTS_VIEW_H_
 #define UI_MESSAGE_CENTER_VIEWS_TOAST_CONTENTS_VIEW_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 86 matching lines @@
   void ClickOnNotificationButton(const std::string& notification_id,
                                  int button_index) override;
   void ClickOnSettingsButton(const std::string& notification_id) override;
 
   // Overridden from gfx::AnimationDelegate:
   void AnimationProgressed(const gfx::Animation* animation) override;
   void AnimationEnded(const gfx::Animation* animation) override;
   void AnimationCanceled(const gfx::Animation* animation) override;
 
   // Overridden from views::WidgetDelegate:
-  views::View* GetContentsView() override;
   void WindowClosing() override;
   void OnDisplayChanged() override;
   void OnWorkAreaChanged() override;
 
   // Recalculates preferred size from underlying view and notifies about it.
   void UpdatePreferredSize();
 
   // Initialization and update.
   void CreateWidget(PopupAlignmentDelegate* alignment_delegate);
 
@@ skipping 27 matching lines @@
 
   gfx::Point origin_;
   gfx::Size preferred_size_;
 
   DISALLOW_COPY_AND_ASSIGN(ToastContentsView);
 };
 
 }  // namespace message_center
 
 #endif // UI_MESSAGE_CENTER_VIEWS_TOAST_CONTENTS_VIEW_H_