Make panels turn on or off shadow effect.

chrome/browser/ui/cocoa/panels/panel_window_controller_cocoa.mm

 // 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.
 
 #include "chrome/browser/ui/cocoa/panels/panel_window_controller_cocoa.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
@@ skipping 905 matching lines @@
     collectionBehavior |= NSWindowCollectionBehaviorCanJoinAllSpaces;
   [[self window] setCollectionBehavior:collectionBehavior];
 }
 
 - (void)enableResizeByMouse:(BOOL)enable {
   if (![self isWindowLoaded])
     return;
   [[self window] invalidateCursorRectsForView:overlayView_];
 }
 
+- (void)showShadow:(BOOL)show {
+  if (![self isWindowLoaded])
+    return;
+  [[self window] setHasShadow:show];
+}
+
 // We have custom implementation of these because our titlebar height is custom
 // and does not match the standard one.
 - (NSRect)frameRectForContentRect:(NSRect)contentRect {
   // contentRect is in contentView coord system. We should add a titlebar on top
   // and then convert to the windows coord system.
   contentRect.size.height += panel::kTitlebarHeight;
   NSRect frameRect = [[[self window] contentView] convertRect:contentRect
                                                        toView:nil];
   return frameRect;
 }
 
 - (NSRect)contentRectForFrameRect:(NSRect)frameRect {
   NSRect contentRect = [[[self window] contentView] convertRect:frameRect
                                                        fromView:nil];
   contentRect.size.height -= panel::kTitlebarHeight;
   if (contentRect.size.height < 0)
     contentRect.size.height = 0;
   return contentRect;
 }
 
 @end