Adds two new observer methods to allow code to be notified when a Window is added/removed from a ...

ui/aura/window_observer.h

Index: ui/aura/window_observer.h
===================================================================
--- ui/aura/window_observer.h	(revision 119986)
+++ ui/aura/window_observer.h	(working copy)
@@ -58,6 +58,12 @@
   // destructor). This is called after the window is removed from its parent.
   virtual void OnWindowDestroyed(Window* window) {}
 
+  // Called when a Window has been added to a RootWindow.
+  virtual void OnWindowAddedToRootWindow(Window* window) {}
+
+  // Called when a Window is about to be removed from a RootWindow.
+  virtual void OnWindowRemovingFromRootWindow(Window* window) {}
+
  protected:
   virtual ~WindowObserver() {}
 };