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

ash/root_window_controller.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_ROOT_WINDOW_CONTROLLER_H_
 #define ASH_ROOT_WINDOW_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "ash/shelf/shelf_types.h"
 #include "ash/system/user/login_status.h"
@@ skipping 62 matching lines @@
   aura::RootWindow* root_window() { return root_window_.get(); }
 
   RootWindowLayoutManager* root_window_layout() { return root_window_layout_; }
 
   WorkspaceController* workspace_controller() {
     return workspace_controller_.get();
   }
 
   ScreenDimmer* screen_dimmer() { return screen_dimmer_.get(); }
 
+  ToplevelWindowEventHandler* panel_container_handler() {
+    return panel_container_handler_.get();
+  }
+
   // Access the shelf associated with this root window controller,
   // NULL if no such shelf exists.
   ShelfWidget* shelf() { return shelf_.get(); }
 
   // Access the shelf layout manager associated with this root
   // window controller, NULL if no such shelf exists.
   ShelfLayoutManager* GetShelfLayoutManager();
 
   // Returns the system tray on this root window. Note that
   // calling this on the root window that doesn't have a launcher will
@@ skipping 97 matching lines @@
   scoped_ptr<ToplevelWindowEventHandler> lock_modal_container_handler_;
   scoped_ptr<ToplevelWindowEventHandler> panel_container_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowController);
 };
 
 }  // namespace internal
 }  // ash
 
 #endif  //  ASH_ROOT_WINDOW_CONTROLLER_H_