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..06978e5f85eb4afcbc56c94e3c429e19d0608e63 100644
--- a/ash/wm/toplevel_window_event_handler.h
+++ b/ash/wm/toplevel_window_event_handler.h
@@ -37,6 +37,10 @@ class ASH_EXPORT ToplevelWindowEventHandler
   explicit ToplevelWindowEventHandler(aura::Window* owner);
   virtual ~ToplevelWindowEventHandler();
 
+  // Pass the WindowResizer to a different ToplevelWindowEventHandler which
+  // will continue the drag.
+  virtual void PassResizer(ToplevelWindowEventHandler* new_owner);
+
   // Overridden from ui::EventHandler:
   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
   virtual void OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
@@ -49,7 +53,7 @@ class ASH_EXPORT ToplevelWindowEventHandler
       aura::client::WindowMoveSource move_source) OVERRIDE;
   virtual void EndMoveLoop() OVERRIDE;
 
-  // Overridden form ash::DisplayController::Observer:
+  // Overridden from ash::DisplayController::Observer:
   virtual void OnDisplayConfigurationChanging() OVERRIDE;
 
  private:
@@ -60,6 +64,8 @@ class ASH_EXPORT ToplevelWindowEventHandler
     DRAG_REVERT
   };
 
+  virtual void AcceptResizer(WindowResizer* resizer, bool in_gesture_drag);
+
   void CreateScopedWindowResizer(aura::Window* window,
                                  const gfx::Point& point_in_parent,
                                  int window_component);