ash: Reorder shutdown of ShelfLayoutManager and StatusAreaWidget

ash/shelf/shelf_widget.cc

 // Copyright 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_widget.h"
 
 #include "ash/ash_switches.h"
 #include "ash/focus_cycler.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_state_delegate.h"
@@ skipping 733 matching lines @@
 void ShelfWidget::SetFocusCycler(FocusCycler* focus_cycler) {
   delegate_view_->set_focus_cycler(focus_cycler);
   if (focus_cycler)
     focus_cycler->AddWidget(this);
 }
 
 FocusCycler* ShelfWidget::GetFocusCycler() {
   return delegate_view_->focus_cycler();
 }
 
-void ShelfWidget::ShutdownStatusAreaWidget() {
+void ShelfWidget::Shutdown() {
+  // Shutting down the status area widget may cause other widgets (e.g. bubbles)
+  // to close, so uninstall the ShelfLayoutManager event filters first.
+  if (shelf_layout_manager_)
+    shelf_layout_manager_->PrepareForShutdown();

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

can you also add comment why we shouldn't remove the shelf layout manager's
observer here?

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

Good catch! Actually, if we reset the shelf_layout_manager_ pointer here we
don't need to be a ShelfLayoutManagerObserver at all!

+
   if (status_area_widget_) {
     Shell::GetInstance()->focus_cycler()->RemoveWidget(status_area_widget_);
     status_area_widget_->Shutdown();
+    status_area_widget_ = nullptr;
   }
-  status_area_widget_ = NULL;
 }
 
 void ShelfWidget::ForceUndimming(bool force) {
   delegate_view_->ForceUndimming(force);
 }
 
 void ShelfWidget::OnWidgetActivationChanged(views::Widget* widget,
                                             bool active) {
   activating_as_fallback_ = false;
   if (active)
@@ skipping 18 matching lines @@
   DCHECK(delegate_view_);
   return delegate_view_->disable_dimming_animations_for_test();
 }
 
 void ShelfWidget::WillDeleteShelf() {
   shelf_layout_manager_->RemoveObserver(this);
   shelf_layout_manager_ = NULL;
 }
 
 }  // namespace ash