Don't reposition if shutdown is in progress

ash/common/wm/overview/window_selector.cc

 // Copyright 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.
 
 #include "ash/common/wm/overview/window_selector.h"
 
 #include <algorithm>
 #include <functional>
 #include <set>
 #include <utility>
@@ skipping 363 matching lines @@
   WmShell::Get()->accessibility_delegate()->TriggerAccessibilityAlert(
       A11Y_ALERT_WINDOW_OVERVIEW_MODE_ENTERED);
 
   UpdateShelfVisibility();
 }
 
 // NOTE: The work done in Shutdown() is not done in the destructor because it
 // may cause other, unrelated classes, (ie PanelLayoutManager) to make indirect
 // calls to restoring_minimized_windows() on a partially destructed object.
 void WindowSelector::Shutdown() {
+  shutdown_ = true;
   // Stop observing screen metrics changes first to avoid auto-positioning
   // windows in response to work area changes from window activation.
   display::Screen::GetScreen()->RemoveObserver(this);
 
   size_t remaining_items = 0;
   for (std::unique_ptr<WindowGrid>& window_grid : grid_list_) {
     for (WindowSelectorItem* window_selector_item : window_grid->window_list())
       window_selector_item->RestoreWindow();
     remaining_items += window_grid->size();
   }
@@ skipping 319 matching lines @@
   for (size_t i = 0; i <= grid_list_.size() &&
                      grid_list_[selected_grid_index_]->Move(direction, animate);
        i++) {
     selected_grid_index_ =
         (selected_grid_index_ + display_direction + grid_list_.size()) %
         grid_list_.size();
   }
 }
 
 }  // namespace ash