Use Ash's ShelfWindowWatcher for app panel windows.

ash/common/shelf/app_list_shelf_item_delegate.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/shelf/app_list_shelf_item_delegate.h"
 
 #include "ash/common/shelf/shelf_model.h"
 #include "ash/common/wm_shell.h"
 #include "base/memory/ptr_util.h"
 #include "grit/ash_strings.h"
@@ skipping 34 matching lines @@
   int title_id;
   title_id = model->status() == ShelfModel::STATUS_LOADING
                  ? IDS_ASH_SHELF_APP_LIST_LAUNCHER_SYNCING_TITLE
                  : IDS_ASH_SHELF_APP_LIST_LAUNCHER_TITLE;
   return l10n_util::GetStringUTF16(title_id);
 }
 
 ShelfMenuModel* AppListShelfItemDelegate::CreateApplicationMenu(
     int event_flags) {
   // AppList does not show an application menu.
-  return NULL;
+  return nullptr;
 }
 
 bool AppListShelfItemDelegate::IsDraggable() {
   return false;
 }
 
 bool AppListShelfItemDelegate::CanPin() const {
   return true;
 }
 
 bool AppListShelfItemDelegate::ShouldShowTooltip() {
   return true;
 }
 
+bool AppListShelfItemDelegate::IsOpen() const {
+  return WmShell::Get()->GetAppListTargetVisibility();
+}
+
 void AppListShelfItemDelegate::Close() {}
 
 }  // namespace ash