ash: Reorder shutdown of ShelfLayoutManager and StatusAreaWidget

ash/wm/aura/wm_shelf_aura.h

 // Copyright 2016 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_WM_AURA_WM_SHELF_AURA_H_
 #define ASH_WM_AURA_WM_SHELF_AURA_H_
 
 #include "ash/ash_export.h"
 #include "ash/shelf/shelf_icon_observer.h"
 #include "ash/shelf/shelf_layout_manager_observer.h"
@@ skipping 24 matching lines @@
   ShelfAlignment GetAlignment() const override;
   ShelfBackgroundType GetBackgroundType() const override;
   void UpdateVisibilityState() override;
   ShelfVisibilityState GetVisibilityState() const override;
   void UpdateIconPositionForWindow(WmWindow* window) override;
   gfx::Rect GetScreenBoundsOfItemIconForWindow(wm::WmWindow* window) override;
   void AddObserver(WmShelfObserver* observer) override;
   void RemoveObserver(WmShelfObserver* observer) override;
 
   // ShelfLayoutManagerObserver:
-  void WillDeleteShelf() override;
+  void WillDeleteShelfLayoutManager() override;
   void OnBackgroundUpdated(wm::ShelfBackgroundType background_type,
                            BackgroundAnimatorChangeType change_type) override;
   void WillChangeVisibilityState(ShelfVisibilityState new_state) override;
 
   // ShelfIconObserver:
   void OnShelfIconPositionsChanged() override;
 
   Shelf* shelf_;
   base::ObserverList<WmShelfObserver> observers_;
   // ShelfLayoutManager is cached separately as it may be destroyed before
   // WmShelfAura.
   ShelfLayoutManager* shelf_layout_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(WmShelfAura);
 };
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_AURA_WM_SHELF_AURA_H_