Attach panel while dragging to bring it in front of other panels.

ash/wm/window_properties.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 ASH_WM_WINDOW_PROPERTIES_H_
 #define ASH_WM_WINDOW_PROPERTIES_H_
 
 #include "ash/ash_export.h"
 #include "ash/wm/property_util.h"
 #include "ui/aura/window.h"
@@ skipping 11 matching lines @@
 
 // Shell-specific window property keys.
 
 // Alphabetical sort.
 
 // A Key to store AlwaysOnTopController per RootWindow. The value is
 // owned by the RootWindow.
 extern const aura::WindowProperty<internal::AlwaysOnTopController*>* const
     kAlwaysOnTopControllerKey;
 
+// A property key to indicate that an in progress drag should be continued
+// after the window is reparented to another container.
+extern const aura::WindowProperty<bool>* const kContinueDragAfterReparent;
+
 // A property key to indicate that the user is cycling through workspaces.
 // The property should only be set on the root window.
 ASH_EXPORT extern const aura::WindowProperty<bool>* const
     kCyclingThroughWorkspacesKey;
 
 // A property key to disable the frame painter policy for solo windows.
 // It is only available for root windows.
 ASH_EXPORT extern const aura::WindowProperty<bool>* const
     kIgnoreSoloWindowFramePainterPolicy;
 
@@ skipping 55 matching lines @@
 // True if the window is controlled by the workspace manager.
 extern const aura::WindowProperty<bool>* const
     kWindowTrackedByWorkspaceKey;
 
 // Alphabetical sort.
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_PROPERTIES_H_