Support detaching/attaching panels via inter-strip drags.

chrome/browser/ui/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/panels/panel_window_controller_cocoa.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
@@ skipping 628 matching lines @@
 }
 
 - (BOOL)canBecomeKeyWindow {
   // Panel can only gain focus if it is expanded. Minimized panels do not
   // participate in Cmd-~ rotation.
   // TODO(dimich): If it will be ever desired to expand/focus the Panel on
   // keyboard navigation or via main menu, the care should be taken to avoid
   // cases when minimized Panel is getting keyboard input, invisibly.
   return windowShim_->panel()->expansion_state() == Panel::EXPANDED;
 }
+
+- (void)setAlwaysOnTop:(bool)onTop {
+  NSWindow* window = [self window];
+  [window setLevel:(onTop ? NSStatusWindowLevel : NSNormalWindowLevel)];
+}
 @end