Use Ash's ShelfWindowWatcher for app panel windows.

ash/common/shelf/app_list_shelf_item_delegate.cc

Index: ash/common/shelf/app_list_shelf_item_delegate.cc
diff --git a/ash/common/shelf/app_list_shelf_item_delegate.cc b/ash/common/shelf/app_list_shelf_item_delegate.cc
index 93b8a10e63ff734b20437f651a85634140fc6569..6fe64b72fe4d48b6cb824b5ed0bfcb8564af3b76 100644
--- a/ash/common/shelf/app_list_shelf_item_delegate.cc
+++ b/ash/common/shelf/app_list_shelf_item_delegate.cc
@@ -52,7 +52,7 @@ base::string16 AppListShelfItemDelegate::GetTitle() {
 ShelfMenuModel* AppListShelfItemDelegate::CreateApplicationMenu(
     int event_flags) {
   // AppList does not show an application menu.
-  return NULL;
+  return nullptr;
 }
 
 bool AppListShelfItemDelegate::IsDraggable() {
@@ -67,6 +67,10 @@ bool AppListShelfItemDelegate::ShouldShowTooltip() {
   return true;
 }
 
+bool AppListShelfItemDelegate::IsOpen() const {
+  return WmShell::Get()->GetAppListTargetVisibility();
+}
+
 void AppListShelfItemDelegate::Close() {}
 
 }  // namespace ash