Fix window shadows.

ui/base/cocoa/underlay_opengl_hosting_window.h

 // Copyright (c) 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.
 
 #ifndef UI_BASE_COCOA_UNDERLAY_OPENGL_HOSTING_WINDOW_H_
 #define UI_BASE_COCOA_UNDERLAY_OPENGL_HOSTING_WINDOW_H_
 #pragma once
 
 #import <Cocoa/Cocoa.h>
 
-// Protocol implemented by windows that need to be informed explicitly about
-// underlay surfaces.
-@protocol UnderlayableSurface
-- (void)underlaySurfaceAdded;
-- (void)underlaySurfaceRemoved;
-@end
-
 // Common base class for windows that host a OpenGL surface that renders under
 // the window. Contains methods relating to hole punching so that the OpenGL
 // surface is visible through the window.
-@interface UnderlayOpenGLHostingWindow : NSWindow<UnderlayableSurface> {
- @private
-  int underlaySurfaceCount_;
-}
-
-// Informs the window that an underlay surface has been added/removed. The
-// window is non-opaque while underlay surfaces are present.
-- (void)underlaySurfaceAdded;
-- (void)underlaySurfaceRemoved;
-
+@interface UnderlayOpenGLHostingWindow : NSWindow
 @end
 
 #endif  // UI_BASE_COCOA_UNDERLAY_OPENGL_HOSTING_WINDOW_H_