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

ash/wm/toplevel_window_event_handler.h

Index: ash/wm/toplevel_window_event_handler.h
diff --git a/ash/wm/toplevel_window_event_handler.h b/ash/wm/toplevel_window_event_handler.h
index 16b4032b2743e3d5882414cd37a2ae7b6f35809c..a0a3ed98b4062d30dc94b3b665a0dafca42d3b5d 100644
--- a/ash/wm/toplevel_window_event_handler.h
+++ b/ash/wm/toplevel_window_event_handler.h
@@ -37,6 +37,8 @@ class ASH_EXPORT ToplevelWindowEventHandler
   explicit ToplevelWindowEventHandler(aura::Window* owner);
   virtual ~ToplevelWindowEventHandler();
 
+  aura::Window* owner() const { return owner_; }

[sky, 2013/03/18 16:17:47]

const aura::Window* owner() const
If you need a non-const version add that too, but it should then be non-const on
both, eg:
aura::Window* owner() { ...

[flackr, 2013/03/20 01:59:32]

Done.

+
   // Overridden from ui::EventHandler:
   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
   virtual void OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
@@ -85,6 +87,9 @@ class ASH_EXPORT ToplevelWindowEventHandler
   // Invoked from ScopedWindowResizer if the window is destroyed.
   void ResizerWindowDestroyed();
 
+  // The container which this event handler is handling events on.
+  aura::Window* owner_;
+
   // Are we running a nested message loop from RunMoveLoop().
   bool in_move_loop_;