Bypass ToplevelWindowEventFilter for panels.

ui/aura/client/window_types.h

 // Copyright (c) 2011 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.
 
 #ifndef UI_AURA_WINDOW_TYPES_H_
 #define UI_AURA_WINDOW_TYPES_H_
 #pragma once
 
 namespace aura {
 namespace client {
 
 // This isn't a property because it can't change after the window has been
 // initialized. It's in client because the Aura Client application derives
 // meaning from these values, not Aura itself.
 enum WindowType {
   WINDOW_TYPE_UNKNOWN = 0,
 
   // Regular windows that should be laid out by the client.
   WINDOW_TYPE_NORMAL,
 
-  // Miscellaneous windows that should not be laid out by the client.
+  // Always on top windows aligned to bottom right of screen.
+  WINDOW_TYPE_PANEL,
+
+  // Miscellaneous windows that should not be laid out by the shell.
   WINDOW_TYPE_POPUP,
 
   WINDOW_TYPE_MENU,
   WINDOW_TYPE_TOOLTIP,
 };
 
 }  // namespace client
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_TYPES_H_