views: Extract Widget observer into its own header file.

ash/system/tray/system_tray_bubble.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_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_
 
 #include "ash/system/tray/tray_bubble_view.h"
 #include "ash/system/user/login_status.h"
 #include "ash/wm/shelf_types.h"
 #include "base/base_export.h"
 #include "base/timer.h"
-#include "ui/views/widget/widget.h"
+#include "ui/views/widget/widget_observer.h"
 
 #include <vector>
 
 namespace ash {
 
 class SystemTray;
 class SystemTrayItem;
 
 namespace internal {
 
 class SystemTrayBubble : public TrayBubbleView::Host,
-                         public views::Widget::Observer {
+                         public views::WidgetObserver {
  public:
   enum BubbleType {
     BUBBLE_TYPE_DEFAULT,
     BUBBLE_TYPE_DETAILED,
     BUBBLE_TYPE_NOTIFICATION
   };
 
   enum AnchorType {
     ANCHOR_TYPE_TRAY,
     ANCHOR_TYPE_BUBBLE
@@ skipping 37 matching lines @@
   void StartAutoCloseTimer(int seconds);
   void StopAutoCloseTimer();
   void RestartAutoCloseTimer();
   void Close();
   void SetVisible(bool is_visible);
   bool IsVisible();
 
  private:
   void CreateItemViews(user::LoginStatus login_status);
 
-  // Overridden from views::Widget::Observer.
+  // Overridden from views::WidgetObserver:
   virtual void OnWidgetClosing(views::Widget* widget) OVERRIDE;
 
   ash::SystemTray* tray_;
   TrayBubbleView* bubble_view_;
   views::Widget* bubble_widget_;
   std::vector<ash::SystemTrayItem*> items_;
   BubbleType bubble_type_;
   AnchorType anchor_type_;
 
   int autoclose_delay_;
   base::OneShotTimer<SystemTrayBubble> autoclose_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayBubble);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_