change the way windows are parented when their parent is set to NULL.

ui/aura/window.h

Index: ui/aura/window.h
===================================================================
--- ui/aura/window.h	(revision 104542)
+++ ui/aura/window.h	(working copy)
@@ -32,6 +32,7 @@
 class KeyEvent;
 class LayoutManager;
 class MouseEvent;
+class ToplevelWindowContainer;
 class WindowDelegate;
 
 namespace internal {
@@ -51,6 +52,9 @@
 
   void Init();
 
+  int type() const { return type_; }
+  void SetType(int type);
+
   int id() const { return id_; }
   void set_id(int id) { id_ = id; }
 
@@ -97,13 +101,18 @@
   void SetParent(Window* parent);
   Window* parent() { return parent_; }
 
-  // Returns true if this Window is the container for toplevel windows.
-  virtual bool IsToplevelWindowContainer() const;
+  // RTTI to a container for top-level windows. Returns NULL if this window is
+  // not a top level window container.
+  virtual ToplevelWindowContainer* AsToplevelWindowContainer();
+  virtual const ToplevelWindowContainer* AsToplevelWindowContainer() const;
 
   // Move the specified child of this Window to the front of the z-order.
   // TODO(beng): this is (obviously) feeble.
   void MoveChildToFront(Window* child);
 
+  // Returns true if this window can be activated.
+  bool CanActivate() const;
+
   // Tree operations.
   // TODO(beng): Child windows are currently not owned by the hierarchy. We
   //             should change this.
@@ -115,6 +124,7 @@
   // Retrieves the first-level child with the specified id, or NULL if no first-
   // level child is found matching |id|.
   Window* GetChildById(int id);
+  const Window* GetChildById(int id) const;
 
   static void ConvertPointToWindow(Window* source,
                                    Window* target,
@@ -206,6 +216,8 @@
   // if |new_show_state| is same as current show state.
   bool UpdateShowStateAndRestoreBounds(ui::WindowShowState new_show_state);
 
+  int type_;
+
   WindowDelegate* delegate_;
 
   ui::WindowShowState show_state_;