ash: Reorder shutdown of ShelfLayoutManager and StatusAreaWidget

ash/shelf/shelf_layout_manager.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/shelf/shelf_layout_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <cstring>
 #include <string>
@@ skipping 243 matching lines @@
   Shell::GetInstance()->
       session_state_delegate()->RemoveSessionStateObserver(this);
   if (root_window_controller_observer_) {
     wm::WmWindowAura::Get(root_window_)
         ->GetRootWindowController()
         ->RemoveObserver(root_window_controller_observer_.get());
   }
 }
 
 void ShelfLayoutManager::PrepareForShutdown() {
+  if (in_shutdown_)
+    return;
+  in_shutdown_ = true;

[oshima, 2016/05/24 20:49:10]

did you actually need this? resetting/removing observer seems to work just fine.

[James Cook, 2016/05/24 21:18:14]

I will need the in_shutdown_ variable in a future CL, but I don't need the if().
I've removed both and I will add back the variable in the next CL.

   // Clear all event filters, otherwise sometimes those filters may catch
   // synthesized mouse event and cause crashes during the shutdown.
   set_workspace_controller(NULL);
   auto_hide_event_filter_.reset();
   bezel_event_filter_.reset();
   // Stop observing window change, otherwise we can attempt to update a
   // partially destructed shelf.
   aura::client::GetActivationClient(root_window_)->RemoveObserver(this);
 }
 
@@ skipping 871 matching lines @@
   UpdateBoundsAndOpacity(target_bounds, true, NULL);
   UpdateVisibilityState();
 }
 
 void ShelfLayoutManager::UpdateShelfVisibilityAfterLoginUIChange() {
   UpdateVisibilityState();
   LayoutShelf();
 }
 
 }  // namespace ash